During our adulescent years, we were loaded with hormones to make or break our prospective mating chances. This is when the body will divert tons of its resources to make us successful in passing on the genes. This was a perfect phase of penile growing. Now, we are just old nuts trying to make the penis larger. Some of us in the 20s, 30s, and 40s that actually go into a secondary phase of penile growth because of the sudden surge of hormones because we are just plain horny during our latter courting period. Old people in their 60s manage to gain penile growth because they always have been horny humans since their youths. The body will provide surges of needed hormones for growths, but we have to do things strategically.
But be warned, what you divert for your penis may be taken from another important area.