I just realised that in session saver, you can make it ask you if you want to save your session as you go to close the window.
This sort of solves the problem of it not warning you when closing multiple tabs because you have to click twice.
It also takes a shorter time for firefox to start now because I don't need to confirm whether or not to restore the previous session.

Thought this might be helpful if you use Session Saver and hadn't discovered this feature already.

I use this but have disabled it asking me.
With this extention closing multiple tabs isn't such a big deal since you can just open it again and everything is fine.

Hmm i only use it so when im upgrading firefox and it has to close (for the binary patch to happen) that i dont loose anything im reading. or if firefox crashes i dont loose my tabs.

it had a really annoying bug that if it crashes after you've sent a POST  to a server then when it reatores your tabs it will resend it (leading to double posts etc)