You know, you're absolutely right. I'm swearing off Firefox. Which browser did you say was as user-configurable as Firefox again?
Until Mozilla's douchebaggery rises to the level of anyone else's, we're all going to sit right here and take the ass-fuckings Moz keeps handing out every few months.
For all data? Probably not, no. For voice and texts? Most desktops could handle a month's worth. For that matter, it's not like there's any need to store it locally when you're sitting in a major telecom hub.
How much non-voice/text data do they capture? No idea. How much do they have access to with zero accountability? All of it.
Look, if you want to think I'm a nutter and live in your happy-la-la land where your government is too busy farting rainbows and unicorns to ever abridge your rights, have at it. The NSA rooms was not rumor-sourced though. That's first hand observation of one instance and friend or family sourced for three more.
I'll grant you I can't give any detail on the rooms but that's primarily because you're not allowed to ask. If you show any interest at all in what they're doing in there you get detained and questioned for several hours then fired. I've seen it happen.