Testicles like to be cooler than the rest of the body
Testicles have to be at a slightly cooler temperature for normal sperm development to take place. Muscles in the scrotum can either contract or relax, to move the testicles closer or farther away from the body and adjust the temperature.
Men produce new sperm throughout life
Unlike women, who are born with all the eggs they'll ever have, men produce new sperm throughout most of their lifetime.
It takes about 3 months for sperm to develop and mature
Sperm require approximately 74 days to mature and up to 20 additional days to become capable of fertilisation
Age – A man's hormone levels decrease with age
With increasing age, testicles do not lose the ability to produce hormones, bu hormone levels do decrease as men age.