They typically get very hot. Under gaming my processor will run about 55C, and the graphics chip (8600 GT) will run 72-75C. The temperatures, IMHO, are enough to burn your unprotected legs. You'll want a strong cooling pad to set it on if you're doing this for long term gaming. Still, you're going to be pushing alot of heat, and with sensitive parts like inverters and stuff, I would say a lifespan of 3 years would be pretty decent at that usage rate. Main thing is to keep the hard drive(s) cool.