Working for a game company we have a lot of laptops under huge load daily we have not had one break so far due to them running hot and breaking. We even had a G4 PowerBook that survived being dropped onto tarmac roads from a car a few times so I would not overly worry as long as you don't play games with your laptop on a blanket or on top of your oven
Finally if the CPU gets too hot the laptop will just shutdown to protect itself.
Edwin
Yeh it usually isn't a problem. Like I said my MBP is running absolutely perfect, just need to investigate the fan issue. I cant say its due to the constant 6000rpm its doing or if its dirt in it. it could be possible the fan is breaking because couple weeks ago it didn't work at all. The hottest my MBP reached was 107°C according to iStat menues. I was like WTF?

but then that doesn't bother me. These machines are built to withstand being under load and if they fail well then ill get it fixed and complain

. I wont stop doing my job or play games occasionally because the computer gets to hot

Some old windows laptops of mine shut down due to high temps

My older 2007 17" with the 8600M GT is also under load like 24/7 doing renderings and that has not had a single problem. Amazing since thousand of people have there dead 8600M GT after doing like nothing

Speaking of G4's, my 17" G4 is still being used intensively and daily. Great machine only added a bigger HDD once thats the only thing that was ever exchanged.