I may fall a little on the paranoid side on this but I sync/backup my phone almost daily and every couple of weeks I'll copy the backup file onto an external hard drive. I only had to use it once but it was definitely worth the efforts as my PC's hard drive died completely at the same time I bought a new phone. After restoring my PC onto a new hard drive from a system image I used an 8 day old backup of the phone to replace the 2 month old system image's file and recovered my phone data into the new phone without a problem. It was definitely worth the efforts of saving a copy of the backup file outside my PC.