He would have lost his sons college thition then. Mitochondrial _inhibition_ is actually more correlated with longevity than the other way around.

If more mitochondria meant more efficient working muscle tissue, then that's what we would have evolved, there's always a compromise. Are you sure you can keep the same power output for a given mass and volume of muscle if you keep increasing mitochondrial numbers? Even the reddit answer clearly says that the heart muscle is rate limited by oxygenation (they have more mitochondria but are also highly vascularized to power the mitochondria). More mitochondria===more power doesn't mean it's better for us, physiology is rarely that simple.