If you got 4.8 and it's stable under prime95 v26.6 small fft's, intel burn test etc while only maxing at 73 under stress - aka, no bsod's or anything, I'd say you got a great cpu. Especially if doing all that at 1.3v. The idle temps are a little warm compared to many I've seen but it depends on the room temp and inside case temps as well. The max temp sounds safe, under 75c and the voltage is within safe ranges. Mine wasn't happy going that high on air, but not sure if a better cooler would help I think my chip's max is around 4.7 so I backed it off to 4.6 to keep similar temps under load (more in the mid to upper 20's at idle) at around 1.285v . Generally 'safe' is considered under 1.4v vcore and closer to 1.3v is even better.
If you do experience any random crashes I'd just ease it back to 4.7 if it were me. Otherwise I don't see any real concern keeping where it's at. Usually when they hit 4.8 the vcore or temps are higher which is more cause for concern.