I'm just about to upgrade my motherboard, CPU, RAM and am buying another hard drive. I have a Coolermaster 850W modular PSU that has done well for the last three and a half years, and am wondering whether I should replace this at the same time. There's nothing wrong with it at the moment and it will comfortably deal with the new kit, but am aware that if it were to go then it would probably take other things with it. How long are these things supposed to last for?
Cooler Master sold three 850W PSUs that have been out for approx. 3yrs or more, the Real Power Pro and Real Power M. And the most likely candidate the Silent Pro M. All three have five year warranties. The SPM has an MTBF of 100,000 hrs, which is ~11 years of continuous use.
So unless you've been seriously abusing it then you will have no problems.