Maybe I'm missing something or set some settings years ago and have forgotten but I have zero problems with restarting Firefox after an update from my package manager.
I regularly have 2-4 Firefox windows with dozens of tabs in each and a "You need to restart" button press takes like 4-5 seconds max to close all windows and reload them all with all of my tabs as they were. The most I have to do is stick each instance on the right workspace.
Granted each tab will reload when opening it but if I'm updating my OS packages I'm probably not exactly "in the zone".
