Creating backups of your hosting account on a DVD is a good way to archive your site offline, however keep in mind that DVD's may not have an everlasting life. 
in those cases we recommend to regulary (say once in the 1 or 2 years,although most say 5 years might work too) make a backup of your backup DVD's to make sure the quality of your backup stays 100% okay.

You can use a dozen of programs to do this, we prefer WinXDVD PRO which is often also can work on disks which are not that great anymore.