Answer :
The physiology of men is in such a way that he can produce semen right from the day he attains puberty and it goes on throughout his life,But still although the production of sperm goes on, the secretion of semen may gradually decrease with age.
well semen semen start secreting after a man achieves puberty from then it continues secretion but the amount of it decreases as a person gets old,it does not stops as far as the man is healthy.But the secretion stops after a person becomes very old.Otherwise it can never be destroyed.