howto/upgrades.md

@@ -104,6 +104,11 @@ Look at the list of packages to be upgraded, and consider upgrading
 them manually, with Cumin (see below), or individually, by logging
 into the host over SSH directly.
 
+Once package upgrades have been dealt with on a host, the alert will clear after
+the timer `prometheus-node-exporter-apt.timer` triggers. It currently runs every
+15 minutes, so it's probably not necessary to trigger it by hand to speed things
+up.
+
 ## Out of date package lists
 
 The `AptUpdateLagging` looks like this: