Re: please read the actual post
Wow! I thought I ran with a lot of tabs open (often 50 or more). You're in the hundreds and maybe topping a 1000 at times. That's definitely in the league where that's so rare the developers aren't going to spend time supporting it.
I doubt you look at every tab every day, there isn't enough time. I guess you're using them more as bookmarks or task recording (ie an open tab is a reminder to do something). Of course you *could* switch to using bookmarks instead but I know what a pain it can be to change your workflow when you already have a way of working.
I'd recommend trying a tab unloader addon such Auto Tab Discard.
https://addons.mozilla.org/en-US/firefox/addon/auto-tab-discard
I've been using it for a while on a laptop to help battery saving and hasn't impeded me at all. It unloads tabs that haven't been looked at in a while (user-definable timeframe), and so killing background scripts which you probably don't care about and freeing up memory. You can whitelist pages for things you want to keep running, eg webmail. Going to the tab will (re)load the page, so a little slower than if it was already loaded, that's the trade-off.