One issue that affects folks with a zillion tabs is that some extensions add a lot of memory usage to every tab. AdBlock Plus is one offender; uBlock Origin is much lighter weight.
Yeh I'm pretty lightweight on extensions, I use only a couple, and uBlock over Adblock. It's just that sites chew through memory over time, and I'm not going to diagnose each one. Firefox already has the feature built in, when you restart the browser, those tabs don't spin up until you access them. They just need to use that functionality on a timer.
In that case, there are some extensions that sleep tabs, and you can use about:memory to figure out which ones are the leakers. Maybe the Firefox crew could figure out how to build this in, it's definitely a case where Chrome's policy means that websites might not fix their leaks because they don't cause problems in Chrome.
