I happen to agree with moldyoldy - use a non-conductive grease. The likelihood of the "heat sink" ( its actually a heat pipe) failing is pretty darn low. The crap heatsink compound is more likely the problem. Recently I dropped my early 2013 MBP retina. Long story. Anyway - for the next few days- machine acted odd - reported USB devices pulling too much current- then it started crashing, and finally started locking up- wouldn't boot until it cooled.I was concerned about having damaged the heat pipe, so pulled it off. The compound was dry and crumbly. Odds are the drop cracked this dry gunk and affected the heat transfer. So I cleaned off the old gunk ( denatured ethanol ) and reassembled using old school white heatsink grease. Grease. As in oily as !&&*, like it has been for the 45 years I've used the stuff. Currently, machine idles at about 110F, and never gets above 215F with all eight hyper threads at full bore. The idle temp is 20F lower than it was new. And will never dry out.