Memes

For me Firefox haven't crashed once in a year or more, even though I'm a heavy user: using it every day for multiple hours as a "tab hoarder", with quite a few addons.

I also rarely restart it, as I don't turn off my computer completely, so the Firefox process is usually as old as the time of last system reboot.

I think you may have ran into a rare bug, that has got persisted in your browser profile.
You may create a new browser profile (e.g. on the about:profiles page) and set your things up there, and most likely it'll be stable.
I think there's also a "refresh Firefox" button somewhere where average people would look for it, but I don't know where it is. But be aware that this will delete everything in Firefox, where's if you create a new profile, the new profile will start with a clean slate and you can switch back and forth between the old one if you find out you need something from there (e.g. old passwords that you haven't transferred, a specific about:config setting if you use those, addon settings, ...), or even have them open at the same time.