In PC environment, I typically replace the hard drive(s) every 3 to 5 years, depending on how critical the data. With my new setup with external drives and the BlacX docks, it's ever so obvious from the flashing red activity light, that drives connected to HRs are getting worked 24x7. What do you do? Wait for the drive to start performing poorly (or go paws up)? Or swap them out on a scheduled basis for a new drive? I'm inclined to swap my external drives every 2-3 years as part of preventative maintenance.