tangor - 8:08 pm on Oct 28, 2011 (gmt 0)
I've never had FF crash on me, but I do things a bit differently (and for different reasons).
I close FF at least once every 24 hours. The cache is cleared at least once every 24 hours. I rarely run more than two tabs open at any time (largest number I've ever had open was 10). I run NoScript (so broken flash or js does not bother me). I run BetterPrivacy so that the few flash items I allow will remove the LSOs during FF shutdown. Always clear the download manager history EACH TIME I DOWNLOAD. Always run the latest version. And, as a result, never run into memory waste/hog. The computer is restarted (warm) Thursday and Sunday, and cold start on Tuesday, but otherwise runs 24/7/365, these are for security reasons in addition to making sure ALL my programs run clean. Computers these days are so quick, this does not take that much time out of my day.
Just observations that no program can stay up "forever". So why try? What works for me may not work for you, but some of these suggestions might solve some problems folks seem to experience.