If I have time later tonight, I'll see if I can't dig up an armorer manual.
TM 9-1005-319-23&P doesn't say anything about excessive wear. The fact is, that nobody really knows the service life of a lot of arts because until recently, few organizations fired their weapons enough to start gathering any data at all. And like I said in my earlier post, records of rounds fired aren't kept on small arms.
The information in the SOPMOD slide show is largely anecdotal. There was a proposal for a round counter for small arms. I'm not sure if anyone ever adopted one.
Firearms are machines. Use them and parts wear. There hasn't been a big push to run out and replace bolts as a prophylactic measure nor has there been a big rush to acquire piston driven weapons except for certain applications (sub 14.5" barrels with suppressors) by certain units.
Jeff