hi, you can also see https://www.servethehome.com/firefox-is-eating-your-ssd-here-is-how-to-fix-it/

One way to reduce disk writes is to reduce the frequency at which Firefox updates your session history file. If you keep a lot of tabs open, this file can be large (mine is over 7 MB). By default, Firefox updates the file as often as every 15 seconds. That way, if Firefox crashes, you'll be able to roll back to the open windows and tabs from that point. You can stretch that out to every 60 seconds, every 3 minutes, etc. Here's how: (1) In a new tab, type or paste '''about:config''' in the address bar and press Enter/Return. Click the button promising to be careful. (2) In the search box above the list, type or paste '''sess''' and pause while the list is filtered (3) Double-click the '''browser.sessionstore.interval''' preference and enter the desired value: * 30000 = every 30 seconds * 60000 = every 60 seconds * 180000 = every 3 minutes * 300000 = every 5 minutes * etc. in milliseconds -- number of seconds followed by 000 ''Please do not edit other session history preferences without researching them first to avoid breaking this feature.'' As for the larger question of "how much is too much" when it comes to writing to your SSD, see this lengthy discussion on Reddit: [https://www.reddit.com/r/firefox/comments/545laq/firefox_is_eating_your_ssd_here_is_how_to_fix_it/]