I didn't read every reply(life's too short) but I think you are on to something.

Jism contains a lot of life force, it is produced obviously by the testes which come under control from the kidneys, which, also are responsible for hair production(and marrow, ect).
Aparently in tantric sex there is a technique where you orgasm but not ejeculate, thus keeping the life force within you.

I'm giving up wanking.....tomorrow lol.