While the game may be demanding of your gpu's, I don't believe you have much to worry about unless your preference of what temp the gpu should be is higher than normal. Those cards can go much higher than it is currently. I wouldn't worry about it, but if it really concerns you so much perhaps you should put a fan on it or upgrade your case. You could always turn some settings down so it doesn't work so hard also. Just sayin'...
Taken from
Nvidia's specs for the GTX285:
Thermal and Power Specs:
Maximum GPU Temperature (in C) 105 C