I always used to backup my .mozilla and .opera folders and carry them on a usb stickto use whenever I tried a new os or reinstalled . This meant that whenever I moved or reinstalled again I would have to backup these folders and copy back. no biggie but as with all backups you could lose any data since your last backup.
What I do now is keep these to folders in my Dropbox folder. Then using dolphin I symbolically link them back to my home folder(as when copying a file , you get a choice , move, copy , link).
Now all my browser activity is automatically backed up instantly.