How often should you backup?
That's a question only you can answer. How many days of data can you afford to do without? Some companies have backups running constantly so they can restore data to the minute. Most computer users don't have that level of need. Decide what's important to you, then create a schedule to backup your data on a daily or weekly basis.
Big Foot MAC Attacked: A Houston, Texas area spark plus company found their Quantum Bigfoot with an Apple operating system would no longer give access to the data. The story began when the drive showed up at our shipping/receiving point unannounced. Following a few telephone calls to learn the circumstances surrounding the failure of the drive, the data recvoery was accomplished and returned to the client in just four days -- including a two-day wait for parts arrival.