When changing a major component on an AR that has been proven as sufficiently reliable for defensive use, such as, the BCG, FCG, lower receiver, or in my case, going from a Carbine H-buffer and 6-Position receiver extension to a Rifle buffer and receiver extension, approximately how many rounds should you put through the gun in its new configuration before judging it re-"vetted" for defensive use?
Do you treat it like a new gun and start the count over again, or is a more cursory test of function good enough when your starting point is a gun that has a history of functioning well?

In my particular case, the Carbine upper in question has actually been on a lower with a Rifle buffer and receiver extension once before a couple years back, and aside from some issues with PMC bronze, was reliable in that configuration. I'm simply going back to that setup because I find I like the way Carbine and Midlength ARs handle and shoot with a fixed A1 length stock.