I used to have an athlon t-bird 1.0 ghz chip that ran @ 62-65C for like 2 years and its still running on a second machine I built for a friend. AMD has a high threshhold for heat capacity (not like intel boooo). IMO, if you're hitting 70+C, do something about it like get a new heatsink or apply thermal compound. Also check to see if you are getting good air flow through your case. A good rule of thumb is 1 intake fan for every 2 exhaust fans.