As updates are checked when I start firefox up, and because there are so many updates, and because I use many plugins, I usually get a request to restart firefox seconds after I start firefox up. This is just as idiotic as what windows itself is doing for it own updates (Windows detected that you moved the mouse, you must reboot for this change to take effect).
Since firefox is regularly restarted anyway, why not simply download the new plugins (or ask) and then do nothing until the next firefox session is started either later the same day or even tomorrow? Firefox shouldn't even ask for it. Just let it happen by itself.
Doing it this way I would be at most a day behind in my updates. without this I am sometimes weeks behind.
Anyway, I switched automatic updates off.
I do check now and then if there are updates, but I admit, not very often.