I once read on a website that eye floaters are caused by too much self-gratification... Sound similar to the "you'll get hairy palms" stuff.
The idea was that it depletes neurotransmitters.
There is also the idea that sperm contains a lot of zinc. Zinc is usually associated to men, while copper is associated to women. I don't know why e
On a short-term basis, from a survival point of view, sex is unnecessary and requires a lot of ressources.
It is very common among athletes (particularly boxers) to not have sex before a competition.