diff --git a/CHANGELOG.md b/CHANGELOG.md
index b88958a..b998698 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -3,6 +3,11 @@ All notable changes to this project will be documented in this file. This change
 
 ## Unreleased
 
+### Added
+
+* Setting to control how many epochs are retained
+* Setting to reset all epochs
+
 ### Changed
 
 * Updated bundled re-frame version to 0.10.3, and bundled reagent version to 0.7.0. This shouldn't impact your project's dependencies as they are source bundled via [mranderson](https://github.com/benedekfazekas/mranderson).
diff --git a/src/day8/re_frame/trace/db.cljs b/src/day8/re_frame/trace/db.cljs
index 5771648..6b0a2bd 100644
--- a/src/day8/re_frame/trace/db.cljs
+++ b/src/day8/re_frame/trace/db.cljs
@@ -11,7 +11,7 @@
         json-ml-paths (localstorage/get "app-db-json-ml-expansions" #{})
         external-window? (localstorage/get "external-window?" false)
         using-trace? (localstorage/get "using-trace?" true)
-        num-epochs (localstorage/get "retained-epochs" 30)
+        num-epochs (localstorage/get "retained-epochs" 5)
         categories (localstorage/get "categories" #{:event :sub/run :sub/create :sub/dispose})]
     (when using-trace?
       (rf/dispatch [:global/enable-tracing]))
diff --git a/src/day8/re_frame/trace/events.cljs b/src/day8/re_frame/trace/events.cljs
index 2d5188d..85316d3 100644
--- a/src/day8/re_frame/trace/events.cljs
+++ b/src/day8/re_frame/trace/events.cljs
@@ -14,8 +14,11 @@
             [day8.re-frame.trace.metamorphic :as metam]
             [re-frame.trace]))
 
+(def default-number-of-epochs-to-retain 5)
+
 (defonce traces (r/atom []))
 (defonce total-traces (r/atom 0))
+(defonce number-of-epochs-to-retain (atom default-number-of-epochs-to-retain))
 
 (defn log-trace? [trace]
   (let [render-operation? (or (= (:op-type trace) :render)
@@ -43,8 +46,16 @@
                                                               (do (reset! total-traces 0)
                                                                   (into [] new2))))
                                                           new))))
-                                             (rf/dispatch [:traces/update-traces @traces])
-                                             (rf/dispatch [:epochs/update-epochs (metam/parse-traces @traces)])))))
+                                             ;; TODO: there is a bit of double handling here, that will be cleaned up
+                                             ;; when the epoch parsing is refactored.
+                                             (let [epochs (metam/parse-traces @traces)
+                                                   retained-epochs (take-last @number-of-epochs-to-retain (:matches epochs))
+                                                   first-id-to-retain (:id (ffirst retained-epochs))
+                                                   new-traces (into [] (drop-while #(< (:id %) first-id-to-retain)) @traces)]
+                                               (reset! traces new-traces)
+                                               (reset! total-traces (count new-traces))
+                                               (rf/dispatch [:traces/update-traces new-traces])
+                                               (rf/dispatch [:epochs/update-epochs {:matches retained-epochs}]))))))
 
 (defn dissoc-in
   "Dissociates an entry from a nested associative structure returning a new
@@ -133,10 +144,13 @@
     ;; TODO: this is not perfect, there is an issue in re-com
     ;; where it won't update its model if it never receives another
     ;; changes after it's on-change is fired.
+    ;; TODO: you could reset the stored epochs on change here
+    ;; once the way they are processed is refactored.
     (let [num (js/parseInt num-str)
           num (if (and (not (js/isNaN num)) (pos-int? num))
                 num
-                30)]
+                default-number-of-epochs-to-retain)]
+      (reset! number-of-epochs-to-retain num)
       (localstorage/save! "retained-epochs" num)
       (assoc-in db [:settings :number-of-epochs] num))))
 
@@ -478,12 +492,11 @@
 
 (rf/reg-event-db
   :epochs/reset
-  [(rf/path [:epochs])]
-  (fn [epochs]
+  (fn [db]
     (re-frame.trace/reset-tracing!)
     (reset! traces [])
     (reset! total-traces 0)
-    nil))
+    (dissoc db :epochs :traces)))
 
 (rf/reg-event-db
   :traces/update-traces
diff --git a/src/day8/re_frame/trace/view/settings.cljs b/src/day8/re_frame/trace/view/settings.cljs
index 7a91541..0a5d5d1 100644
--- a/src/day8/re_frame/trace/view/settings.cljs
+++ b/src/day8/re_frame/trace/view/settings.cljs
@@ -97,8 +97,7 @@
                     num-traces @(rf/subscribe [:traces/number-of-traces])
                     epochs-to-retain (rf/subscribe [:settings/number-of-retained-epochs])]
 
-                ;; TODO: retain last
-                #_[settings-box
+                [settings-box
                  [[rc/h-box
                    :align    :center
                    :gap      horizontal-gap
@@ -118,7 +117,7 @@
                                :label [rc/v-box
                                        :align :center
                                        :children ["clear all epochs"]]
-                               :on-click #(println "Clicked CLEAR")]]]]
+                               :on-click #(rf/dispatch [:epochs/reset])]]]]
                  [[:p num-epochs " epochs currently retained, involving " num-traces " traces."]]
                  settings-box-81])
 
@@ -194,7 +193,7 @@
                 [[:p "Most of the time, low level trace is noisy and you want it filtered out."]]
                 settings-box-131])
 
-              #_[rc/line]
+              [rc/line]
               [settings-box
                [[rc/button
                  :class "bm-muted-button app-db-panel-button"