Playing Solitaire I see a spike of 3c over idle when the cards all spring off.
So have I. That's why I don't run at 3.6.
Long term I would think it would be but published high is 62c. Is it?
Acceptable speed is what speed/temp/voltage combination you accept. I've hit 4G long enough to pull up Speedfan and see 60c at 1.675v. I *run* a 720 at 3.33/1.4v with 4 cores. 29 idle, 38c after all 4 cores have been under 100% load for an hour.
Find out the published max's for your model CPU at www.google.com. Try not to exceed them too much/often.
Get heatpipes.