I would be very uncomfortable running my cards at 85+C 24/7. It wont instantly kill the cards, but electromigration may wear them out quite fast if you are unlucky. Everyone has their personal limit, I know Im anal about temps, but 70C is my feel good limit and Im no where near that. My 5850s are ~60C @ 900 MHz, my 5870 is even sub 50C (though admittedly, because of an absolute overkill Spitfire cooler)
All of them are dead silent. (5850 twin frozr stock cooler @45%, the other 5850 has a 6 euro Battle-axe cooler).
Even more importantly, run GPU-Z and have a look at your VRM temperatures under load. Depending what kind of VRMs and VRM cooling is used, they can be as high as 100+C or as low at 60C. Not all cards support VRM monitoring, but definitely check if yours do, because overheating VRMs are probably the number 1 cause of dead gpu's.
If the card does not support VRM temp monitoring, that means a non reference design, and Im under the impression most non reference cards have VRMs dont overheat as easily a reference cards, but thats just an impression I have. If you want to be sure, consider buying an IR thermometer.