When does sperm reach maturity?
Heifers reach sexual maturity by 10 to 12 months of age, though this depends on the breed. Bulls reach sexual maturity around 8 to 9 months of age, though this too depends on the breed. Late maturing breeds reach sexual maturity later than average (10 to 12 months); Early maturing breeds reach sexual maturity earlier than average (7 to 9 months).
The body evolved for sexual activity. It is necessary to have sex to continue the species. Sperm and semen are used in that process, and the male body produces millions of sperm, most of which are disposed of if they reach maturity without being used. It will not weaken your body to "lose" semen or sperm. It is there to be used.