Also best not to let the history get to big or it will slow things down so don't make too many days.
Then if you want to you can open your history and highlight the day or sites you want to and right click and delete them. That way you just keep a history on sites you want the history on like forums.

May want to get MozBackup 1.4.5 http://mozbackup.jasnapaka.com/

Great for backups and restore of...

MozBackup is a simple utility for creating backups of
Mozilla Firefox, Mozilla Thunderbird, SeaMonkey,
Mozilla Suite and Netscape profiles.

It allows you to backup and restore bookmarks, mail,
contacts, history, extensions, cache etc.

The history is not something your really want to backup but this will do it for you.
This can also be added to another computer and you can do a backup on the one PC and then take it to the other PC and do a restore.
Note: some plugins and extensions may still need to be reinstalled if your doing a restore on a new profile.
Also on the backups are saved as a .pcv file type "Firefox 1.5.0.12 (en-US) - 2007-06-20.pcv" and you can rename the .pvc to .zip and open them too.