ATI says 95°C is okay but it may not run clean either. I had an ASUS XT-PE that ran at 80C stone stock in the 3DM01se Nature torture loop. While they say it is okay there is a catch to running hot.
For every 10°C you increase a discrete parts (memory chips, cores, Mosfets, IC's, etc) average operating temperature you cut its lifespan in 1/2 what ever that given lifespan may be. Conversely for every 10°C you lower the average operating temperature you double the parts lifespan. It doesn't take a rocket scientist to conclude that a card that runs 60C will have an average life span that is 4 times longer than if the same card runs 80°C.
The above is the reason that a properly modded card can have a longer lifespan that the same card will stock.
John