Bad option: yearly
I don't think it's coincidence that "yearly" has zero votes. If that's how often you back up, you are probably going to answer "infrequently", "I knew I was forgetting something", or "when it's too late", because at least 2 of those 3 apply.
I don't think it's coincidence that "yearly" has zero votes
Actually, I backup yearly. My personal stuff, and for a good reason:
On the first day of every year, one of my hard disks has headcrashed. This has become a certainty, and given that I never wanted to turn to superstition (and switch off the machines over night or on New Year's Day holiday which might just save some money), I back up everything early on new years eve. That saves time in early January.
I backup things at work nearly all the time.
And of course, wolfger is right, every year aplies to be "infrequently", so I had considered checking that option.