There was an old rule for range guns. At 100,000 rounds M10s needed a tune up. Not sure if that was true or not, but its a good place to start considering it. Of course in the past it was just cheaper to replace the old gun with a newer one.
We've often postulated that a normal man (or woman) couldn't wear out a K22 in his/her lifetime. Of course you probably could if you dedicated your life to it, and a pot full of money. I'd guess a k22 would be getting pretty loose by 250,000. With heavy recoiling guns, like 44 Magnums, and if shot with overloads, life would be much shorter.
Lots of different considerations, too. N frame guns with admittedly more serious calibers seem to get loose faster. It might also be related to essentially the same size parts moving a heavier cylinder.
Automatics sometimes wear their springs faster. Lots of potential causes, mostly related to cheaper manufacturing methods and the constant pounding of full power loads. Exceptions abound. Try wearing out a SIG P210 sometime. I've read about european guns with a half million round counts having some small cracks in the frame. You know what a half million rounds cost?
There are some little hints if you don't want yours to wear out. Try cleaning it. And even applying some good lubricants. Regularly.