I would say the consensus from our gas heater experts is that the brass ASME header is not worth the additional cost on a residential pool nor is the cupronickel heat exchanger. Water chemistry and proper pool care are far more determinant of heater lifetime than the composition of those components. If you have corrosive unbalanced pool water, then no heater will last. A standard MasterTemp 400 will last a long time if your pool water is properly managed.