I haven't had my cards for very long, I have the OC windforce edition. But I did try once to OC the cards by 10%, stock they run 1100/1500. And I had a blue screen straight away, it was odd because it wouldn't have had time to overheat that quickly.
But also I found something very odd, find a game that's already high end, go manually in the drivers set everything to 16xEQ, 16AF, high quality and multisampling and see if you cards start to really increase in temps. Mine are cooking atm
97 degrees with the fan on 100%