I would welcome with open arms and tears of joy a Firefox release that could survive a day -- heck, even half a day -- without crashing. It's such a joy to come back from grabbing a cub of coffee or lunch to find that I have to restart effin' Firefox and reload all my tabs again.
Have you considered that maybe it's you, not Firefox? Have you got flaky plugins installed? Or flaky extensions? Some extensions have been known not to play nice with others.
I use Firefox heavily every day (always on the latest release) and I haven't had it crash in literally years. Nor have I found it a memory hog. As I type this I have 10 different sites open and Firefox is using ~400 meg.