One of the most important things you can do with regards to your data is to make regular backups. You never know when something may happen to it. Many things can go wrong such as it can become corrupted, mistakenly deleted, or the computer may get a virus, crash, or even be stolen or subject to some other catastrophe. One never knows when this will occur and it can create a definite sinking feeling when it does!
In addition to making backups and having an off-site storage location for periodic backups, it is imperative that you confirm from time to time that the data is indeed being backed up. Just because you have inserted the cd, thumb drive, or whatever backup media you choose, it does not guarantee that a good copy of the data is being stored on it. This should be tested on occasion to confirm so you are not left with an unfortunate surprise should you need to restore the backup.