I think it's absolutely fine with those temps. I have a Brisbane X2 5400+ running Prime95 SmallFTT over 65C@3.2ghz for 8hours. I lowered the clock down to 3ghz, and it's still ticking along just fine today. Typical usage won't get temps over 58C. My cooler is Zalman 9500a.
Stress test your overclock for an extended time and if it passes you should be fine.