> caveat emptor: when firefox upgrades it usually wont change these settings for you

It's not so bad. You can sort prefs by user-defined, they're in bold, and each one has a reset-to-default option.

Also you can do a whole browser reset which preserves only passwords/bookmarks. Instructions: https://support.mozilla.org/en-US/kb/refresh-firefox-reset-a...

And firefox profiles might be handy for this too (from the command line add --ProfileManager or -P <profile name>).