Hard Disks are unpredictable as they're mechanical - and not just mechanical, but microscopically so, with high-speed componentry and plenty of constant vibration.Generally speaking, hard disks have warranty periods of 1, 3 or 5 years (manufacturer, model and revision dependent) so add about 1 year to that and this will indicate roughly what the manufacturer thinks it should last (basically, at the end of the warranty period, prepare to move your data to a new medium).Of course, how it's used during it's life is also a contributing factor. I've seen some disks die within weeks of purchase, others last the better part of a decade.
