I don't think it's true, i don't feel the need to have sex all the time and when a situation is there that i could i don't.
I Think it really depends on who you are and if you view sex as if it's a porche ( You wouldn't lend a porche to anybody besides your wife, it is special)
OR as a Hyundai ( Cheap , doesn't mean much and you lend it to whoever wanted it.)
I think that in both cases you can't generalize on it