That would be a bug. I use it all day with hundreds of tabs (sometimes thousands, but I'm getting better about pruning back) and don't see this. I know many, many people who could say the same.

If you have time, please file it: https://bugzilla.mozilla.org/enter_bug.cgi . If you're willing, include a profile ( https://profiler.firefox.com is pretty easy to use). You can look at about:performance (or in newer versions, about:processes, but I don't think that's in release yet.) When you file the bug, you will probably be asked if it still happens in safe mode (which would probably blame an addon).

> If I leave it running for too long with a bunch of tabs open, it will eat more and more of my CPU until it's hogging it all.

That's not normal Firefox behavior. I run multiple windows (one in each monitor), each of them with many dozens of tabs and only time I ever quit Firefox is if I have to reboot the machine for an update, so it runs for many months on end. Never seen this runaway CPU consumption.

> so it runs for many months on end

Danger. You want to restart it more frequently than this for updates.

I've been using it for the last 2 years. both on linux and windows, works ok on the later, but on linux I keep getting random corrupted graphics / black screens each time ram/swap are almost full. looking into filled bugs this doens't seems to be something new, I can find some bug reports dating back to 6 years and no sugestions for a fix beside disabling hardware acceleration, which doesn't work for me at least.