It's very important that you create backups for your websites. Some hosts even automatically create backups that you can easily download at any time from you control panel. I personally think it's best to make your own backups, that way if there's ever an issue with the automatic backup you still have a offline one. I try to backup my websites once every week or so. How about you? Do you go out your way to make backups and how often do you create backups? I typically only make database backups of my sites though too, I'm sure it's probably best to backup the whole site just in case if your theme gets broken at some point I suppose.