If you backup to a hard drive, you can simply swap your main and backup drives every now and then. If you have three drives, you can always be using one as main, one as local backup, and the third locked up offsite as the "house burns down" backup. Then swap the offsite and local backups every month.

I'm just starting to do this and it feels great. I thought about the money I pay for renters insurance, and then I realized that something much harder to replace than my furniture and other physical possessions was vulnerable not only to fire/natural disaster but plain old disk failure.