If you’re still using FF2 you should immediately stop what you’re doing and upgrade to FF3. I say this with the confidence of someone who has been using FF3 for a few months now.
The key advantages: it’s fast and spares your RAM.
Operational speed is amazing in this version. It’s so good that I have (at least temporarily) given up on Flock because FF3’s new engine is so much faster. I have no hard metrics for you quants to chew on, but all the anecdotal evidence I’ve accumulated is compelling.
Second: memory usage is way more optimized. I could have never kept 15 or 20 tabs open in FF2, but in FF3 I do it all the time. It’s to the point where I am about to begin looking around for a tab management plugin because I have so many open tabs during typical usage. My total memory debt right now with about 15 tabs open is 188 MB, and it’s stable.