You can achieve the same effect by reusing the profile, though I've heard it can be buggy due to forwards/backwards compatibility issues esp. in add-ons. It req

You can achieve the same effect by reusing the profile, though I've heard it can be buggy due to forwards/backwards compatibility issues esp. in add-ons. It requires a bit of technical effort (launching firefox with the -P flag to open the profile manager, or editing profiles.ini directly), but if you're using several versions of Firefox chances are this is not a problem.