I have a 12 year old Compaq that still works fine, but admittedly it hasn't been used frequently for many years now. I also put together a PC 3 years go and I had used ULTRA PSU (I believe 600watt) which went bad only after couple of years of use. I think it depends on the work load, power settings, and where you store your PC will also have big influence how well your hardwares cope over time. I put together a brand new desktop 6 months ago for my garage, from fans to cd roms things started to go bad. I think the breakdown had a lot to do with moisture, drastic temp difference between day and night, and dusts building up overtime.