I've always had ATI Graphics cards , mostly made by Sapphire
An never had a problem with any of them. (the old drivers wern't much cop though)
The later CPUs are running faster with faster FSBs and running more sophisticated programs demanding faster graphics. This pushes the laws of physics & electronics closer and closer to the limit. The closer to the limit the hotter we all get. Keep you stuff cool and it'll run for ever.
Personally I use liquid cooling, CPU, NORTHBRIDGE and GPU. all running at 30 degress
whilst overclocking a 2.5 Mhz to 3.2 GMhz and the FSB 400Mhz, ATI 9800 pro
Oh...
I turn my system off when I'm not using it. (trying to save the planet and all

)
Steve (a techy...)