2 things kill electronics:
1) Voltage transients (spikes)(like lightning)
2) Heat
I run my fans full speed unless my charger is not plugged in and Im doing something really light/non intensive.
I have one of the older MBPs with the faulty video cards and have never had a problem. As a matter of fact I have not had one single problem since Ive had the laptop (coming up on 2 years). Maybe its a coincidence but I doubt it. I also keep an eye on my temps and allow them to cool if they go higher than ~60
-You want your temperatures as low as possible.
-Apple would like to sell you another computer sooner rather than later.
-Apple allows their temperature threshold on their laptops to be higher so the computer will run quiet...nice but it will harm it over time.