You can disable Firefox's "an update is available" nag dialog with about:config app.update.silent=true.
This pref has been available in Firefox for a long time, but I believe it wasn't enabled because people who don't restart their browser often would not get security updates in a timely manner.
This pref has been available in Firefox for a long time, but I believe it wasn't enabled because people who don't restart their browser often would not get security updates in a timely manner.