I am thinking about picking up a better cpu cooler to achieve 4.8+ on my I7 2700k.
70C on synthetics, gets iffy above that
Synthetic bench marks? Like prime 95, intel burn?
yeah, its okay for it to get to get like 75C for a minute but don't let it get past 80C, that's when it starts to decrease lifespan
85 under Prime95, small FFT, max.
Currently with my hyper 212 evo, sp120s 2350 rpm fans, and mx4 my cores sit in the 50s at full load and will at times just touch 60c. This at 1.28 volts at 4.5ghz on an asus z77.
CPU throttles at 95c so stick well below that as best you can. Some may say stay below 80, others 70, its up to you. Just note that if you havent got decent airflow in your case, with high cpu temps getting dumped and not exhausted everyother component will heat up as well.
After having a few sandys and still using one i suggest that the max safe vcore for these chips are around 1.3v region, that being said, intel states that the max 'VID' is 1.52 and many say that around 1.4 if your on air and 1.45 should be the max if your running water cooling. Personally I will not go above 1.5v for 24/7 with these chips due to the silicon degradation.
Fingers crossed you have won the silicon lottery and have a nice chip that does 4.8 @ f'all volts.