That's true. However, the AKs have longer part life, especially with the low pressure 7.62x39 cartridge. Barrels go past 30,000 rounds.
Q Part life is completely dependent on the quality of the steel used to manufacture either firearm. I would say both AKs and ARs of equal part quality would last about the same round count. With the AKs piston rod and ARs gas valve failing first.
Barrel life is dependent largely on throat erosion, which is different with different cartridges. AR-15s don't have a "gas valve." You don't know what you're talking about. I don't know of any recorded instances of the AK piston breaking.
You'd lose the barrel and a fucking bolt lug long before that