Comment 4 for bug 35043

I like the current situation (save not enabled by default). Users probably don't expect their session to be saved... I have seen lots of beginners opening dozens of windows (15 firefox instances for example), and it's very fortunate that leaving the session allows a small automatic "clean up" to take place.

If you want your session saved, you can always switch the option on, but I believe that most people won't want this.