I had the problem at some point, that Firefox wouldn't start anymore after an upgrade (at ~7,5k). That's was when I gave up, and fed all tabs to the one-tab extension, which saves them as links and closes the tabs. Nowadays I regularly press its save-and-close-all button, so the number of tabs stays reasonable (less than 200 or so).
Haha, I use session buddy for that but I reopen all tabs every time I restart my computer because the fallacious thinking of "THIS time I'll go through some of them!" My above comment did prompt me to seriously start looking into a better system, though predictably now I have a ton of tabs open for linkding, archivy, et al. The awesome-$THING project(s) are great resources but you quickly spawn fifty additional tabs for each project's repo
