it might not be unusual, but I believe it to be a bit of a consipiracy on ATIs part (nV are also guilty but to a lesser extent)
When your GPU runs that high, it degrades faster, meaning your card will not last as long
I admit most of us will replace our cards regularly (every year or so) so its not such a problem in the short term, but when it comes to selling our kit, its not so easy as its usually on its way out
Ultimately it means that consumers buy more cards, more often which results in more money for the card makers.. Revenues are up for them (maybe not after the credit crunch) as people are buying more cards as more of them are going tits up (read any hardware forum and youll get what Im talking about)
This is why I believe in water cooling as a valid and long term cost effective solution to this problem.. It might cost me more on the setup and require more maintenance, but I will have better cards and parts when it comes to selling them on

The most valid arguement I can think of that shows what I'm talking about is Duracell batteries (excluding digital cameras as they dont seem to last in those at all)
you can pop off to the market and buy 4 AA batteries for a quid, and youll use those quite quickly.. for example, 10 hours in a device, but you could also pop off to tesco for some duracells that will cost you maybe £3 that will last 40 hours in that same device.. so you get 33% more power for the cost.. which ultimately means you spend less money in the long term.