I email frequently, store important documents in Thunderbird and maintain a large list of contact and groups. If (somehow) your mozilla profile gets corrupted, your data goes bye-bye. Firefox stores settings that may be important to you as well, like your favorites.
Aside from having backups to protect your data, MozBackup provides an easy way to backup and restore your profile if you upgrade your computer. Simply run MozBackup to back up your Firefox and Thunderbird profiles, transfer the saved file to your new computer, then restore the backup (again using MozBackup).
Like magic, all your emails, contacts, history, extensions and favorites remain intact. Oh, did I say it works for Mozilla Sunbird, Flock, SeaMonkey, Mozilla Suite, Spicebird, Songbird and Netscape profiles? It does.
It’s small, portable, free, very simple to use, and it works flawlessly. I’ve been using it for years. I couldn’t live without it.