It seems Richard Campbell has been successful at keeping mango trees small yet productive, and he considers that the ideal. Also, commercial growers with intensive operations keep their trees small, don't they? On the other hand, certain vigorous varieties don't take to that type of regimen so it would hurt their productivity. As far as impacting the health and life expectancy of the tree, I don't see how that would be the case. There are bonsai trees that are hundreds of years old! Anyway, that's my two cents.