I have installed a lot of addons and recently I find that Firefox keeps increasing memory usage and sometimes hangs after 30 minutes running.
It's hard to test them one by one. Is there a better way to test them?
Remove half of them (32/2=16). Still unstable: the next half, else, the other half.
32-16-8-4-2-1 => 6 steps.
Does not seem to be possible. If you want something that will show firefox memory usage in firefox, see here.
In my experience, anytime I add more than a few add-ons to Firefox, the chances for conflicts and crashes are multiplied greatly. I would say pick the add-ons that are the most useful to you, and if you must, add on one at a time and give it time to see if the browser becomes unstable.
Another possibility is that it is time to do a fresh install of your OS. Any pc slows down to a crawl and browsers crash frequently when the system has not been restored for a maximum of say, a year, sometimes six months. This is a not-advertised dirty little secret of the Windows OS. It is full of leaky code which will fill up your hard drive even though you have ALL your files stored in the cloud on a service like Dropbox. A disk clean up will do NOTHING to free up space or solve this problem. Your pc will only become slower and slower, prompting many to think it's time for a new pc, when all you need is a fresh install.
Research elsewhere for how to save all your add-ons and settings in one nifty file for transfer to a clean OS.
As well, your multiple add-ons are bound to have pieces of conflicting code, which may operate fairly well together for a time, but by the same token, will build up detritus in your system and start to cause you more and more problems. So you MAY be able to start over with a fresh install, cannot guarantee.