It has been known for a long time among multiple cultures that Semen Retention is a gate way to health, morality, success and spirituality. It was for this reason that for a long time, both men and women practiced celibacy before marriage, and only indulge in sex infrequently, unlike the current generation.
In case of health, if one looks at Vedic literature and current modern experiments, just like our hair which grows to a certain length after which stops growing, once the semen in the body reached to the maximum amount then it will be used for other body parts to develop and strengthen. So from evolution our body is designed to procreate as the primary aspect of life, and then later it is prioritized for aspects like muscle strength, bone health etc. If one keeps ejaculating, the health of the individual deteriorates very fast. This was observed by the yogis/hermits/sufis, and thus they channeled their inner strength towards better health, mind and spiritual needs.
Also when men engage in sports or other physical activities, they refrain from sex for a longer periods or before any major event, to avoid diverting their attention and strength. When one participates in sex or masturbation a portion of vital energy is expended, and the man is less able to be focused on his activities, which leads to failure. So it is very important that men preserve their semen to better attain their goals and aspirations. This can be extended to mental activities as well.
The world we live in today, where people are more morally corrupt, and lack courage, virtue has been forgotten regarding promiscuity or masturbation. Whenever humans engage in lust, societies are bound to crumble. Virtuous societies endured in the past because they chose to go against the urge of sex.
One can easily corroborate this as humanity is pushed forward by individuals in the field of art, music, philosophy, virtue and science by individuals who are celibate or almost bachelors. This can be noticed in Ramakrishna Paramahamsa, Swami Vivekananda, Jesus Christ, the Wright Brothers, Nicola Tesla, Socrates, Leonardo Da Vinci, et al. Such individuals have tremendous courage, photographic memory, incredible concentration, highly intelligent and become masters at their chosen paths in life.
So, it is imperative that men resist their biological urges to a large extent, and instead of wasting time in the pursuit of empty pleasures, try to retain semen as much as you can. In marriage, once you have couple of children its better to refrain from frequent sexual pleasures as much as possible and focus on retaining your semen for once betterment of health, success and spiritual needs.