diff --git a/example/Main.hs b/example/Main.hs
new file mode 100644
--- /dev/null
+++ b/example/Main.hs
@@ -0,0 +1,69 @@
+{-# LANGUAGE OverloadedStrings #-}
+{-# LANGUAGE NumericUnderscores #-}
+{-# LANGUAGE CPP #-}
+import           System.Metrics.Prometheus.Ridley
+import qualified System.Metrics.Prometheus.Metric.Gauge as P
+import qualified System.Metrics.Prometheus.RegistryT as P
+import           System.Metrics.Prometheus.Ridley.Types
+import           Lens.Micro
+import           Web.Spock
+import           Web.Spock.Config
+import           Network.Wai.Metrics
+import           Control.Exception
+import           Control.Monad.Trans
+import           Data.Time.Clock.POSIX
+import           Katip
+import           System.IO
+
+spockWeb :: RidleyCtx -> IO ()
+spockWeb ctx = do
+  spockCfg <- defaultSpockCfg () PCNoDatabase ()
+  runSpock 8080 (spock spockCfg (app ctx))
+
+app :: RidleyCtx -> SpockCtxM ctx conn sess st ()
+app ctx = do
+  case ctx ^. ridleyWaiMetrics of
+    Nothing -> return ()
+    Just m  -> middleware (metrics m)
+  get root $ text "Hello World!"
+  get "ping" $ text "pong"
+
+customExpensiveMetric :: RidleyMetric
+customExpensiveMetric =
+  CustomMetric "my-expensive" (Just $ 60 * 1_000_000) get_metric
+  where
+    get_metric :: MonadIO m => RidleyOptions -> P.RegistryT m RidleyMetricHandler
+    get_metric opts = do
+        m <- P.registerGauge "current_time" (opts ^. prometheusOptions . labels)
+        return $ mkRidleyMetricHandler "current_time" m update False
+
+    update :: P.Gauge -> Bool -> IO ()
+    update gauge _ = do n  <- getPOSIXTime
+                        tn <- getCurrentTime
+                        putStrLn $ "Updating time, at " <> show tn
+                        P.set (realToFrac n) gauge
+
+customCrashfulMetric :: RidleyMetric
+customCrashfulMetric =
+  CustomMetric "my-crashful" (Just $ 60 * 1_000_000) get_metric
+  where
+    get_metric :: MonadIO m => RidleyOptions -> P.RegistryT m RidleyMetricHandler
+    get_metric opts = do
+        m <- P.registerGauge "crashful" (opts ^. prometheusOptions . labels)
+        return $ mkRidleyMetricHandler "crashful" m (\_ _ -> throwIO $ userError "CRASH!!") False
+
+main :: IO ()
+main = do
+#if MIN_VERSION_katip(0,8,0)
+    let onlyErrors i = pure $ Katip._itemSeverity i >= Katip.DebugS
+    ridleyScribe <-
+      Katip.mkHandleScribe Katip.ColorIfTerminal stdout onlyErrors Katip.V2
+#else
+    ridleyScribe <-
+      Katip.mkHandleScribe Katip.ColorIfTerminal stdout Katip.DebugS Katip.V2
+#endif
+    let opts = newOptions [("service", "ridley-test")] (customExpensiveMetric : customCrashfulMetric : defaultMetrics)
+             & prometheusOptions . samplingFrequency .~ 5
+             & dataRetentionPeriod .~ Just 60
+             & katipScribes .~ ("RidleyTest", [("stdout", ridleyScribe)])
+    startRidley opts ["metrics"] 8729 >>= spockWeb
diff --git a/ridley.cabal b/ridley.cabal
--- a/ridley.cabal
+++ b/ridley.cabal
@@ -1,13 +1,13 @@
 name:                ridley
-version:             0.3.2.1
+version:             0.3.3.0
 synopsis:            Quick metrics to grow your app strong.
-description:         Please see README.md
+description:         A collection of Prometheus metrics to monitor your app. Please see README.md
 homepage:            https://github.com/iconnect/ridley#README
 license:             BSD3
 license-file:        LICENSE
 author:              Alfredo Di Napoli & the IRIS Connect Engineering Team
 maintainer:          chrisd@irisconnect.co.uk
-copyright:           2017 IRIS Connect Ltd.
+copyright:           2022 IRIS Connect Ltd.
 category:            Web
 build-type:          Simple
 data-files:
@@ -19,6 +19,11 @@
      default: False
      description: Enable -Werror
 
+flag library-only
+  description: Build without the executable, for downstream packages
+  manual: True
+  default: True
+
 library
   hs-source-dirs:      src
   include-dirs:        include
@@ -29,8 +34,10 @@
                        System.Metrics.Prometheus.Ridley.Metrics.CPU
                        System.Metrics.Prometheus.Ridley.Metrics.Network
                        System.Metrics.Prometheus.Ridley.Metrics.Network.Types
+  other-modules:       System.Metrics.Prometheus.Ridley.Types.Internal
 
   build-depends:       async < 3.0.0,
+                       auto-update >= 0.1,
                        base >= 4.7 && < 5,
                        containers < 0.7.0.0,
                        katip < 0.9.0.0,
@@ -38,9 +45,10 @@
                        template-haskell,
                        ekg-core,
                        time,
-                       text,
+                       text >= 1.2.4.0,
                        mtl,
                        shelly,
+                       safe-exceptions < 1.8,
                        transformers,
                        prometheus > 0.5.0 && < 2.3.0,
                        raw-strings-qq,
@@ -85,6 +93,23 @@
                      , http-client >= 0.4.30
   ghc-options:         -threaded -rtsopts -with-rtsopts=-N
   default-language:    Haskell2010
+
+executable ridley-example
+    main-is: example/Main.hs
+    if !flag(library-only)
+      build-depends: base
+                   , time
+                   , ridley
+                   , katip
+                   , text
+                   , wai-middleware-metrics
+                   , Spock
+                   , microlens
+                   , mtl
+                   , prometheus
+    if flag(library-only)
+      buildable: False
+    default-language:    Haskell2010
 
 source-repository head
   type:     git
diff --git a/src/System/Metrics/Prometheus/Ridley.hs b/src/System/Metrics/Prometheus/Ridley.hs
--- a/src/System/Metrics/Prometheus/Ridley.hs
+++ b/src/System/Metrics/Prometheus/Ridley.hs
@@ -2,6 +2,8 @@
 {-# LANGUAGE BangPatterns #-}
 {-# LANGUAGE TemplateHaskell #-}
 {-# LANGUAGE OverloadedStrings #-}
+{-# LANGUAGE NumericUnderscores #-}
+{-# LANGUAGE RecordWildCards #-}
 {-# LANGUAGE CPP #-}
 module System.Metrics.Prometheus.Ridley (
     startRidley
@@ -22,9 +24,11 @@
   , defaultMetrics
   ) where
 
+import           Control.AutoUpdate as Auto
 import           Control.Concurrent (threadDelay, forkIO)
 import           Control.Concurrent.Async
 import           Control.Concurrent.MVar
+import qualified Control.Exception.Safe as Ex
 import           Control.Monad (foldM)
 import           Control.Monad.IO.Class (liftIO, MonadIO)
 import           Control.Monad.Reader (ask)
@@ -32,12 +36,12 @@
 import           Data.IORef
 import qualified Data.List as List
 import           Data.Map.Strict as M
-import           Data.Monoid ((<>))
 import qualified Data.Set as Set
 import           Data.String
 import qualified Data.Text as T
 import           Data.Time
 import           GHC.Conc (getNumCapabilities, getNumProcessors)
+import           GHC.Stack
 import           Katip
 import           Lens.Micro
 import           Network.Wai.Metrics (registerWaiMetrics)
@@ -55,6 +59,7 @@
 import           System.Metrics.Prometheus.Ridley.Metrics.Memory
 import           System.Metrics.Prometheus.Ridley.Metrics.Network
 import           System.Metrics.Prometheus.Ridley.Types
+import           System.Metrics.Prometheus.Ridley.Types.Internal
 import           System.Remote.Monitoring.Prometheus
 
 --------------------------------------------------------------------------------
@@ -74,9 +79,18 @@
   opts <- ask
   let popts = opts ^. prometheusOptions
   let sev   = opts ^. katipSeverity
+  le <- getLogEnv
   case x of
-    CustomMetric metricName custom -> do
-      customMetric <- lift (custom opts)
+    CustomMetric metricName mb_timeout custom -> do
+      customMetric <- case mb_timeout of
+        Nothing   -> lift (custom opts)
+        Just microseconds -> do
+          RidleyMetricHandler mtr upd flsh lbl cs <- lift (custom opts)
+          doUpdate <- liftIO $ Auto.mkAutoUpdate Auto.defaultUpdateSettings
+                        { updateAction = upd mtr flsh `Ex.catch` logFailedUpdate le lbl cs
+                        , updateFreq   = microseconds
+                        }
+          pure $ RidleyMetricHandler mtr (\_ _ -> doUpdate) flsh lbl cs
       $(logTM) sev $ "Registering CustomMetric '" <> fromString (T.unpack metricName) <> "'..."
       (customMetric :) <$> (registerMetrics xs)
     ProcessMemory -> do
@@ -152,7 +166,7 @@
 
         liftIO $ do
           lastUpdate <- newIORef =<< getCurrentTime
-          updateLoop <- async $ handlersLoop lastUpdate handlers
+          updateLoop <- async $ handlersLoop le' lastUpdate handlers
           putMVar x updateLoop
 
         lift $ P.sample >>= serveMetrics port path
@@ -165,8 +179,8 @@
           $(logTM) ErrorS (fromString $ show e)
         Right _ -> return ()
 
-    handlersLoop :: IORef UTCTime -> [RidleyMetricHandler] -> IO a
-    handlersLoop lastUpdateRef handlers = do
+    handlersLoop :: LogEnv -> IORef UTCTime -> [RidleyMetricHandler] -> IO a
+    handlersLoop le lastUpdateRef handlers = do
       let freq = opts ^. prometheusOptions . samplingFrequency
       let flushPeriod = opts ^. dataRetentionPeriod
       mustFlush <- case flushPeriod of
@@ -180,8 +194,8 @@
               return True
             False -> return False
       threadDelay (freq * 10^6)
-      updateHandlers (List.map (\x -> x { flush = mustFlush }) handlers)
-      handlersLoop lastUpdateRef handlers
+      updateHandlers le (List.map (\x -> x { flush = mustFlush }) handlers)
+      handlersLoop le lastUpdateRef handlers
 
 serveMetrics :: MonadIO m => Int -> P.Path -> IO RegistrySample -> m ()
 #if (MIN_VERSION_prometheus(2,2,2))
@@ -191,5 +205,16 @@
 #endif
 
 --------------------------------------------------------------------------------
-updateHandlers :: [RidleyMetricHandler] -> IO ()
-updateHandlers = mapM_ runHandler
+updateHandlers :: LogEnv -> [RidleyMetricHandler] -> IO ()
+updateHandlers le hs = mapM_ (\h@RidleyMetricHandler{..} -> runHandler h `Ex.catchAny` (logFailedUpdate le label _cs)) hs
+
+logFailedUpdate :: LogEnv -> T.Text -> CallStack -> Ex.SomeException -> IO ()
+logFailedUpdate le lbl cs ex =
+  runKatipContextT le () "errors" $ do
+      $(logTM) ErrorS $
+        fromString $ "Couldn't update handler for "
+                  <> "\"" <> T.unpack lbl <> "\""
+                  <> " due to "
+                  <> Ex.displayException ex
+                  <> " originally defined at "
+                  <> prettyCallStack cs
diff --git a/src/System/Metrics/Prometheus/Ridley/Metrics/CPU/Darwin.hs b/src/System/Metrics/Prometheus/Ridley/Metrics/CPU/Darwin.hs
--- a/src/System/Metrics/Prometheus/Ridley/Metrics/CPU/Darwin.hs
+++ b/src/System/Metrics/Prometheus/Ridley/Metrics/CPU/Darwin.hs
@@ -1,3 +1,4 @@
+{-# LANGUAGE OverloadedStrings #-}
 {-# LANGUAGE QuasiQuotes #-}
 {-# LANGUAGE TemplateHaskell #-}
 module System.Metrics.Prometheus.Ridley.Metrics.CPU.Darwin
@@ -5,7 +6,6 @@
   , processCPULoad
   ) where
 
-import           Data.Monoid ((<>))
 import qualified Data.Vector.Storable as V
 import qualified Data.Vector.Storable.Mutable as VM
 import           Foreign.C.Types
@@ -37,8 +37,4 @@
 
 --------------------------------------------------------------------------------
 processCPULoad :: (P.Gauge, P.Gauge, P.Gauge) -> RidleyMetricHandler
-processCPULoad g = RidleyMetricHandler {
-    metric = g
-  , updateMetric = updateCPULoad
-  , flush = False
-  }
+processCPULoad g = mkRidleyMetricHandler "ridley-process-cpu-load" g updateCPULoad False
diff --git a/src/System/Metrics/Prometheus/Ridley/Metrics/CPU/Unix.hs b/src/System/Metrics/Prometheus/Ridley/Metrics/CPU/Unix.hs
--- a/src/System/Metrics/Prometheus/Ridley/Metrics/CPU/Unix.hs
+++ b/src/System/Metrics/Prometheus/Ridley/Metrics/CPU/Unix.hs
@@ -43,8 +43,4 @@
 
 --------------------------------------------------------------------------------
 processCPULoad :: (P.Gauge, P.Gauge, P.Gauge) -> RidleyMetricHandler
-processCPULoad g = RidleyMetricHandler {
-    metric = g
-  , updateMetric = updateCPULoad
-  , flush = False
-  }
+processCPULoad g = mkRidleyMetricHandler "ridley-process-cpu-load" g updateCPULoad False
diff --git a/src/System/Metrics/Prometheus/Ridley/Metrics/DiskUsage.hs b/src/System/Metrics/Prometheus/Ridley/Metrics/DiskUsage.hs
--- a/src/System/Metrics/Prometheus/Ridley/Metrics/DiskUsage.hs
+++ b/src/System/Metrics/Prometheus/Ridley/Metrics/DiskUsage.hs
@@ -84,11 +84,7 @@
 
 --------------------------------------------------------------------------------
 diskUsageMetrics :: DiskUsageMetrics -> RidleyMetricHandler
-diskUsageMetrics g = RidleyMetricHandler {
-    metric = g
-  , updateMetric = updateDiskUsageMetrics
-  , flush = False
-  }
+diskUsageMetrics g = mkRidleyMetricHandler "ridley-disk-usage" g updateDiskUsageMetrics False
 
 --------------------------------------------------------------------------------
 mkDiskGauge :: MonadIO m => P.Labels -> DiskUsageMetrics -> DiskStats -> P.RegistryT m DiskUsageMetrics
diff --git a/src/System/Metrics/Prometheus/Ridley/Metrics/Memory.hs b/src/System/Metrics/Prometheus/Ridley/Metrics/Memory.hs
--- a/src/System/Metrics/Prometheus/Ridley/Metrics/Memory.hs
+++ b/src/System/Metrics/Prometheus/Ridley/Metrics/Memory.hs
@@ -32,8 +32,4 @@
 
 --------------------------------------------------------------------------------
 processMemory :: P.Gauge -> RidleyMetricHandler
-processMemory g = RidleyMetricHandler {
-    metric = g
-  , updateMetric = updateProcessMemory
-  , flush = False
-  }
+processMemory g = mkRidleyMetricHandler "ridley-process-memory" g updateProcessMemory False
diff --git a/src/System/Metrics/Prometheus/Ridley/Metrics/Network/Darwin.hs b/src/System/Metrics/Prometheus/Ridley/Metrics/Network/Darwin.hs
--- a/src/System/Metrics/Prometheus/Ridley/Metrics/Network/Darwin.hs
+++ b/src/System/Metrics/Prometheus/Ridley/Metrics/Network/Darwin.hs
@@ -12,7 +12,6 @@
 import           Control.Monad
 import           Control.Monad.IO.Class
 import qualified Data.Map.Strict as M
-import           Data.Monoid ((<>))
 import qualified Data.Text as T
 import           Foreign.C.String
 import           Foreign.C.Types
@@ -167,11 +166,7 @@
 
 --------------------------------------------------------------------------------
 networkMetrics :: NetworkMetrics -> RidleyMetricHandler
-networkMetrics g = RidleyMetricHandler {
-    metric = g
-  , updateMetric = updateNetworkMetrics
-  , flush = False
-  }
+networkMetrics g = mkRidleyMetricHandler "ridley-network-metrics" g updateNetworkMetrics False
 
 --------------------------------------------------------------------------------
 mkInterfaceGauge :: MonadIO m => P.Labels -> NetworkMetrics -> IfData -> P.RegistryT m NetworkMetrics
diff --git a/src/System/Metrics/Prometheus/Ridley/Metrics/Network/Unix.hs b/src/System/Metrics/Prometheus/Ridley/Metrics/Network/Unix.hs
--- a/src/System/Metrics/Prometheus/Ridley/Metrics/Network/Unix.hs
+++ b/src/System/Metrics/Prometheus/Ridley/Metrics/Network/Unix.hs
@@ -70,11 +70,7 @@
 
 --------------------------------------------------------------------------------
 networkMetrics :: NetworkMetrics -> RidleyMetricHandler
-networkMetrics g = RidleyMetricHandler {
-    metric = g
-  , updateMetric = updateNetworkMetrics
-  , flush = False
-  }
+networkMetrics g = mkRidleyMetricHandler "ridley-network-metrics" g updateNetworkMetrics False
 
 --------------------------------------------------------------------------------
 mkInterfaceGauge :: MonadIO m => P.Labels -> NetworkMetrics -> IfData -> P.RegistryT m NetworkMetrics
diff --git a/src/System/Metrics/Prometheus/Ridley/Types.hs b/src/System/Metrics/Prometheus/Ridley/Types.hs
--- a/src/System/Metrics/Prometheus/Ridley/Types.hs
+++ b/src/System/Metrics/Prometheus/Ridley/Types.hs
@@ -1,10 +1,10 @@
-{-# LANGUAGE ExistentialQuantification #-}
-{-# LANGUAGE RankNTypes #-}
-{-# LANGUAGE GeneralizedNewtypeDeriving #-}
 {-# LANGUAGE DeriveFunctor #-}
+{-# LANGUAGE ExistentialQuantification #-}
 {-# LANGUAGE FlexibleInstances #-}
-{-# LANGUAGE TypeSynonymInstances #-}
+{-# LANGUAGE GeneralizedNewtypeDeriving #-}
+{-# LANGUAGE RankNTypes #-}
 {-# LANGUAGE TemplateHaskell #-}
+{-# LANGUAGE TypeSynonymInstances #-}
 module System.Metrics.Prometheus.Ridley.Types (
     RidleyT(Ridley)
   , Ridley
@@ -16,7 +16,12 @@
   , PrometheusOptions
   , RidleyMetric(..)
   , RidleyOptions
-  , RidleyMetricHandler(..)
+  , RidleyMetricHandler
+  , metric
+  , updateMetric
+  , flush
+  , label
+  , mkRidleyMetricHandler
   , defaultMetrics
   , newOptions
   , prometheusOptions
@@ -32,27 +37,31 @@
 import           Control.Monad.Reader (MonadReader)
 import           Control.Monad.Trans.Class
 import           Control.Monad.Trans.Reader
-import           Data.Monoid
 import qualified Data.Set as Set
 import qualified Data.Text as T
 import           Data.Time
+import           GHC.Stack
 import           Katip
 import           Lens.Micro.TH
 import           Network.Wai.Metrics (WaiMetrics)
 import qualified System.Metrics.Prometheus.MetricId as P
 import qualified System.Metrics.Prometheus.RegistryT as P
 import           System.Remote.Monitoring.Prometheus
+import           System.Metrics.Prometheus.Ridley.Types.Internal
 
 --------------------------------------------------------------------------------
 type Port = Int
 type PrometheusOptions = AdapterOptions
 
---------------------------------------------------------------------------------
-data RidleyMetricHandler = forall c. RidleyMetricHandler {
-    metric       :: c
-  , updateMetric :: c -> Bool -> IO ()
-  , flush        :: !Bool
-  -- ^Whether or net to flush this Metric
+mkRidleyMetricHandler :: forall c. HasCallStack
+                      => T.Text
+                      -> c -> (c -> Bool -> IO ()) -> Bool -> RidleyMetricHandler
+mkRidleyMetricHandler lbl c runC flsh = withFrozenCallStack $ RidleyMetricHandler {
+    metric       = c
+  , updateMetric = runC
+  , flush        = flsh
+  , label        = lbl
+  , _cs          = popCallStack callStack
   }
 
 --------------------------------------------------------------------------------
@@ -64,7 +73,17 @@
                   | Wai
                   | DiskUsage
                   -- ^ Gets stats about Disk usage (free space, etc)
-                  | CustomMetric T.Text (forall m. MonadIO m => RidleyOptions -> P.RegistryT m RidleyMetricHandler)
+                  | CustomMetric !T.Text
+                                 -- ^ The name of the metric
+                                 !(Maybe Int)
+                                 -- ^ An optional timeout, in microseconds,
+                                 -- that regulates how often the metric is
+                                 -- actually updated. If Nothing, the metric
+                                 -- will be updated using Ridley top-level setting,
+                                 -- if 'Just' the underlying 'IO' action will be run
+                                 -- only every @n@ seconds, or cached otherwise.
+                                 (forall m. MonadIO m => RidleyOptions -> P.RegistryT m RidleyMetricHandler)
+                                 -- ^ An action to generate the handler.
                   -- ^ A user-defined metric, identified by a name.
 
 instance Show RidleyMetric where
@@ -74,7 +93,7 @@
   show Network               = "Network"
   show Wai                   = "Wai"
   show DiskUsage             = "DiskUsage"
-  show (CustomMetric name _) = "Custom@" <> T.unpack name
+  show (CustomMetric name _ _) = "Custom@" <> T.unpack name
 
 instance Eq RidleyMetric where
   (==) ProcessMemory ProcessMemory             = True
@@ -83,7 +102,7 @@
   (==) Network Network                         = True
   (==) Wai     Wai                             = True
   (==) DiskUsage DiskUsage                     = True
-  (==) (CustomMetric n1 _) (CustomMetric n2 _) = (==) n1 n2
+  (==) (CustomMetric n1 _ _) (CustomMetric n2 _ _) = (==) n1 n2
   (==) _ _                                     = False
 
 instance Ord RidleyMetric where
@@ -120,14 +139,14 @@
     Wai                    -> LT
     DiskUsage              -> EQ
     _                      -> GT
-  compare (CustomMetric n1 _) xs = case xs of
+  compare (CustomMetric n1 _ _) xs = case xs of
     ProcessMemory          -> LT
     CPULoad                -> LT
     GHCConc                -> LT
     Network                -> LT
     Wai                    -> LT
     DiskUsage              -> LT
-    (CustomMetric n2 _)    -> compare n1 n2
+    (CustomMetric n2 _ _)    -> compare n1 n2
 
 --------------------------------------------------------------------------------
 data RidleyOptions = RidleyOptions {
@@ -160,10 +179,10 @@
 
 --------------------------------------------------------------------------------
 runHandler :: RidleyMetricHandler -> IO ()
-runHandler (RidleyMetricHandler m u f) = u m f
+runHandler (RidleyMetricHandler m u f _ _) = u m f
 
 --------------------------------------------------------------------------------
-newtype RidleyT t a = Ridley { unRidley :: ReaderT RidleyOptions t a }
+newtype RidleyT t a = Ridley { _unRidley :: ReaderT RidleyOptions t a }
   deriving (Functor, Applicative, Monad, MonadReader RidleyOptions, MonadIO, MonadTrans)
 
 type Ridley = RidleyT (P.RegistryT (KatipContextT IO))
diff --git a/src/System/Metrics/Prometheus/Ridley/Types/Internal.hs b/src/System/Metrics/Prometheus/Ridley/Types/Internal.hs
new file mode 100644
--- /dev/null
+++ b/src/System/Metrics/Prometheus/Ridley/Types/Internal.hs
@@ -0,0 +1,23 @@
+{-# LANGUAGE BangPatterns #-}
+{-# LANGUAGE ExistentialQuantification #-}
+module System.Metrics.Prometheus.Ridley.Types.Internal
+  ( RidleyMetricHandler(..)
+  ) where
+
+import           GHC.Stack
+import qualified Data.Text as T
+
+--------------------------------------------------------------------------------
+data RidleyMetricHandler = forall c. RidleyMetricHandler {
+  -- | An opaque metric
+    metric       :: c
+  -- | An IO action used to update the metric
+  , updateMetric :: c -> Bool -> IO ()
+  -- | Whether or not to flush this Metric
+  , flush        :: !Bool
+  -- | A user-friendly label, used to report errors
+  , label        :: !T.Text
+  -- | A CallStack, for precise error reporting
+  , _cs          :: CallStack
+  }
+