diff --git a/src/yggdrasil/router.go b/src/yggdrasil/router.go
index 5a6eb45..d2a8c43 100644
--- a/src/yggdrasil/router.go
+++ b/src/yggdrasil/router.go
@@ -101,6 +101,8 @@ func (r *router) mainLoop() {
 				// Any periodic maintenance stuff goes here
 				r.core.switchTable.doMaintenance()
 				r.core.dht.doMaintenance()
+				r.core.sessions.cleanup()
+				r.core.sigs.cleanup()
 				util_getBytes() // To slowly drain things
 			}
 		case f := <-r.admin:
diff --git a/src/yggdrasil/session.go b/src/yggdrasil/session.go
index b36349a..8631ff2 100644
--- a/src/yggdrasil/session.go
+++ b/src/yggdrasil/session.go
@@ -89,7 +89,8 @@ func (s *sessionInfo) timedout() bool {
 // Sessions are indexed by handle.
 // Additionally, stores maps of address/subnet onto keys, and keys onto handles.
 type sessions struct {
-	core *Core
+	core        *Core
+	lastCleanup time.Time
 	// Maps known permanent keys to their shared key, used by DHT a lot
 	permShared map[boxPubKey]*boxSharedKey
 	// Maps (secret) handle onto session info
@@ -111,6 +112,7 @@ func (ss *sessions) init(core *Core) {
 	ss.byTheirPerm = make(map[boxPubKey]*handle)
 	ss.addrToPerm = make(map[address]*boxPubKey)
 	ss.subnetToPerm = make(map[subnet]*boxPubKey)
+	ss.lastCleanup = time.Now()
 }
 
 // Gets the session corresponding to a given handle.
@@ -202,13 +204,6 @@ func (ss *sessions) createSession(theirPermKey *boxPubKey) *sessionInfo {
 	sinfo.send = make(chan []byte, 32)
 	sinfo.recv = make(chan *wire_trafficPacket, 32)
 	go sinfo.doWorker()
-	// Do some cleanup
-	// Time thresholds almost certainly could use some adjusting
-	for _, s := range ss.sinfos {
-		if s.timedout() {
-			s.close()
-		}
-	}
 	ss.sinfos[sinfo.myHandle] = &sinfo
 	ss.byMySes[sinfo.mySesPub] = &sinfo.myHandle
 	ss.byTheirPerm[sinfo.theirPermPub] = &sinfo.myHandle
@@ -217,6 +212,19 @@ func (ss *sessions) createSession(theirPermKey *boxPubKey) *sessionInfo {
 	return &sinfo
 }
 
+func (ss *sessions) cleanup() {
+	// Time thresholds almost certainly could use some adjusting
+	if time.Since(ss.lastCleanup) < time.Minute {
+		return
+	}
+	for _, s := range ss.sinfos {
+		if s.timedout() {
+			s.close()
+		}
+	}
+	ss.lastCleanup = time.Now()
+}
+
 // Closes a session, removing it from sessions maps and killing the worker goroutine.
 func (sinfo *sessionInfo) close() {
 	delete(sinfo.core.sessions.sinfos, sinfo.myHandle)
diff --git a/src/yggdrasil/signature.go b/src/yggdrasil/signature.go
index 374183a..203c9ad 100644
--- a/src/yggdrasil/signature.go
+++ b/src/yggdrasil/signature.go
@@ -71,16 +71,20 @@ func (m *sigManager) isChecked(key *sigPubKey, sig *sigBytes, bs []byte) bool {
 func (m *sigManager) putChecked(key *sigPubKey, newsig *sigBytes, bs []byte) {
 	m.mutex.Lock()
 	defer m.mutex.Unlock()
-	now := time.Now()
-	if time.Since(m.lastCleaned) > 60*time.Second {
-		// Since we have the write lock anyway, do some cleanup
-		for s, k := range m.checked {
-			if time.Since(k.time) > 60*time.Second {
-				delete(m.checked, s)
-			}
-		}
-		m.lastCleaned = now
-	}
-	k := knownSig{key: *key, sig: *newsig, bs: bs, time: now}
+	k := knownSig{key: *key, sig: *newsig, bs: bs, time: time.Now()}
 	m.checked[*newsig] = k
 }
+
+func (m *sigManager) cleanup() {
+	m.mutex.Lock()
+	defer m.mutex.Unlock()
+	if time.Since(m.lastCleaned) < time.Minute {
+		return
+	}
+	for s, k := range m.checked {
+		if time.Since(k.time) > time.Minute {
+			delete(m.checked, s)
+		}
+	}
+	m.lastCleaned = time.Now()
+}