What if I don't want to autoupdate? Why should a browser which was working just fine one day stop working the next, just because Mozilla released a new version?

What if I don't want to autoupdate? Why should a browser which was working just fine one day stop working the next, just because Mozilla released a new version? Why does a new version release kill an already installed existing version? Also, an update (auto or manual) means restarting the browser, which logs me out of my sessions, profile, and password manager.