Earlier quoted context omitted.
Firefox will suspend running pages when it is unmapped, so I put it on its own virtual desktop and only switch to that desktop when I need a webpage.
And, if you're like me and have dozens of tabs open for weeks on end, the OneTab extension is pretty awesome too.
I'm using "Auto Tab Discard" and I'm happy with it. It "unloads" the unused tabs and reloads them once you switch back to them.