My routine: I have two 150 GB drives in a RAID 0. I do an image backup nightly to an internal 2 TB drive, takes about 1/2 hour. I set the software to keep 10 copies, it rolls off the oldest. Weekly backup to an NAS. The wife's computer follows the same routine, except that she backs up an 80 GB single drive to a 500 GB internal nightly, then the weekly backup to the same NAS.
I have restored my machine twice from image backups. ^