I feel like it needs to go through 250 rounds reliably from a state of being clean. Why that criteria? My carry gun has match grade components and is very tight, which is conductive to excellent accuracy. It also means that after 250-300 rounds of range ammo stuff gets sticky, though I never had it malfunction, it gets slow. I keep my gun clean, and since I don't carry 300 rounds with me, it's unlikely I'll shoot it to the point of malfunction.
Some may feel my little test isn't enough, but since I'm not on a battlefield, I believe it's plenty. Few of us carry enough ammo for an extended firefight, even in our vehicle, and you have a better chance of hitting the lotto and being struck by lightning on the same day than getting into such an encounter.
'Merica: Back to back World War Champs