So you've had your browser use >2G of VM? I know I sure haven't and I do browse with a lot of tabs. And with browsers moving to a process-per-tab model it matters even less since each tab will have it's own VM.
I couldn't imagine how many tabs it would take to use >2GB. Just yesterday I had 19 tabs open in Opera (64bit), with well over 100 closed tabs, in a session that was open more than 24 hours, and it was only using ~700MB total. I'm sure it's possible, I just can't imagine it.
FWIW, I do have 64-bit Flash installed now, and it's not any better than the 32-bit version was.