but then firefox will end up using well over a gigabyte of ram.
Even at it's worst, I've never seen FF get that bad, although I believe that it does happen, if for no other reason than I've heard it reported so often.
Out of curiosity, what plugins are you using? What's the use case?
You mention having up to 50 tabs open, and I think the most I'll hit is about 25, 30 on the extreme side of things. I wonder if there's a "tipping point" of open tabs that things just start to go on a runaway...