The temperature is above 38 Celsius degrees in Greece these days. However, my PS3 still works like a charm even if it's turned on for 8+ hours straight. I have to admit that it gets really warm on the upper and rear sides but this doesn't seem to affect the functionality.
My wife asked me to view our digcam pictures, and i said.. "hey, why dont we try to use PS3.." and there was, i slotted in the MS card in, and keep PS3 closed inside the TV rack without any ventilation (only small holes for cables).
Ran it for about an hour full of laughing, after finish, i tried to shut it down, and i realize how much heat it was inside the rack. It was like opening an oven.
But the console still worked fine, and I continue playing game after that, with TV rack's door open.