I don't know about outsmarting the engineers, but I know these little facts:
1. my new iMac 24" 2.8 Ghz with default settings is running in excess of 70 degrees centigrade for power supply (like 78 at high load) - and default fan control does not do anything about it - fan speed stays at lowest setting.
2. When I raise the lowest default fan speed a little (from 1200 to 1500 or 2000 for CPU fan, which also cools the power supply) - I manage to keep my power supply within 60 degrees at all times.
3. I don't have factual knowledge of how long my power supply is going to last if operated at 70C and above, but my guess is that keeping it below 60 WILL PROLONG ITS LIFE!
also remember that smart engineers only care about 1 year warranty period, while I care a bit further into the future!