That's true too. Like I said, it's a sweet-spot between too low and too high. Mine was raised as a market turkey until it was about 3 months when we started to lower protein, but mine was never supposed to stick around after fair either so we didn't start him out trying to extend his lifespan
Lower protein, but it's hard to find the sweetspot since they still need protein for their bones to be strong enough to support their weight. Also not free feeding them
If you keep their growth rate slow, it's likely to live a year or two. Mine was 3, but he had loads of health issues back shortly after 6 months. He really should have been processed back then.