I was on the SiG Forum, and one of the members there was talking about a thread here where some gun rental shop in Las Vegas had started a thread on what they saw as the best performing AR's, parts, lube's and pretty much everything that had to do with the gun and maintenance.
A few things jumped out at me ... No piston guns had a longer life expectancy a DI gun, and they typically lasted 2x longer. An HK-416 they bought, didn't last as long as typical mid-grade builds did; the barrel was shot out at 10,000 rounds; just about every other barrel, semi or full auto would last around 20,000 before they started key-holing except JT barrels, they lasted 60,000+ rounds ... From what I read of the article (he had edited it) that was one of the biggest surprises ... Of lubes they were all about equal as long as you followed the manufacturers instructions, which basically said to run it wet ... However they did see less "misting" with Slip2000 when the gun got hot ... Lastly, LMT bolts typically lasted a little longer than generic mil-spec bolts but not long enough to warrant their higher price ... To the best of my remembry, nothing was mentioned of any other premium guns like KAC's