He's got many points.
And I'm finally home to test the OP's concern. It is definitely valid in regards to two of my configurations, both involving a 285 GTX.
Lowered all settings including resolution and in-game settings except Physics (but in Windowed mode). From 44 degrees C, in-game I'm at 70 degrees C in 10 min.
Slid the General Drawing Settings alone to readable text, reached 84 degrees C in 10 min. Fan crept up 3%.
It's fairly cold outside, but as it get's warmer, I worry what will happen to this poor little beast.
But yes, now that I think about it, SE doesn't develop for the PC, they port console titles to the PC.
NVidia sandwiches running hot.