dont know if this was mentioned in this thread, but the ONLY reason 360s have overheated are because of the massive power supply blocks
.. if you are ONE OF THE RARE PEOPLE
to get freezing in-game because of over-heating all you would need to do is suspend that power block in mid-air.. in other words tie it to a string and have it hanging in mid-air or put it on top of a box with the lid open so that heat can escape from it from all sides
... READ THIS:
SOLUTION TO XBOX360 OVERHEATING
and i dont think anyones 360 has overheated to the point where it stopped working altogether.. so i dont see any need to go out and buy any extra fans..