speakin on bio chemical terms, potential for the human tissue to grow is a rate limting step based upon genetic make-up (DNA)..
therefore, as our bodies age, cells get older, less cells reproduce, the rate limiting step increases therefore slowing down protein synthesis..
Hormones play a big factor since GH and test begin to decline with age. Therefore, yes one can fully hit their genetic potential at their respective age...its not fair to say that your genetic potential is the same at age 24 than it is at 54...your DNA already has you planned out on how your body will change/decrease/increase at various stages of your life.
yeah i'm a science nerd..holla