In the nvidia control panel under temp settings there is a max temperature, for my 6800U it is 115C, 90C is warmish, I presume you are using stock cooling, but unless you reach your max temp you should be OK, even if you do manage to reach your max temp the card will throttle to reduce the temp or just plain shut down.
A suggestion ..... if you wish to continue to oc your card look for a suitable third party gpu cooler (I have a zalman but there are plenty of others out there)
See my sig for my stock and oc clocks, I never exceed 80C under load, even at 475/1280