More people are starting to comment on how Firefox is becoming a slow browser, with all the Add-Ons and the time it take to start up. I have found this too. I think that over time your profile acquires lots of settings and little bits of code here and there, left over from add-ons you may or may not be still using. The best way to deal with this, as with many computer problems is to wipe out and start again. This doesn’t mean I suggest you loose all your saved passwords and bookmarks though.
When I did this with my Firefox profile (which was many years old), I did it the manual way. It didn’t take me long, but you would need to know what you’re doing. I have since found a Firefox Add-On called FEBE (install from here) which will automate the process for you. Although IMHO, you still need to give it some thought when you are changing its settings. You can back up so many things from your profile with this, that you could end up defeating the object of clearing house! Remember, our aim here, is it wipe out as much of your old profile as possible without loosing the things you really need, like your bookmarks, passwords and Add-Ons.
You can set a schedule for FEBE, set whatever suits you. I am trying out having it do a back up everytime I shutdown Firefox, this does slow things down though. You can set daily, weekly or monthly backups. Or even just schedule a reminder to tell you to do it manually.
My recommended settings for saving the most important things with FEBE are in the above screen shot.
Now, in the event that you need to rebuild your Firefox profile due to some sort of fault and malfunction, that is still in your FEBE backup, then you need to manually rebuild your profile. *Deep breath*, this is going to take a little while, but follow my instructions and you’ll get there.