Inn to be less interested in sex with someone after becoming attached?

I've never had that happen. Once I get more attached to the person and develop a strong bond of trust, we tend to get more experimental because we're comfortable talking about fetish together at that point.

Yes, many many many people are wired like that. In order to have sexual excitement they need distance. Once they are "comfy" and "close" it excitement goes away.
You cannot have excitement with stability. Too bad huh?

Because the cold relationship hints your brain to make up for it through sex.

You're just emotionally weak.

Sex is one thing and love and respect another.
You can love,respect and be emotional attached to your girlfriend but you cant bring all that to bed if you want real good sex. If you want good sex leave the emotional part behind and after you fuck, after you can again be emotional again.
Guys do have to split both things to be able to please themselves and their girlfriends.
Women are different. A women if not emotional attached to a guy she can't do good sex.
Once you split both things your problem ends. Age helps.

Hey. Look up Madonna-whore complex.

no. testosterone ebbs in long term, committed relationships. as opposed to being relatively high in new relationships. fact.

Why buy the cow..... when you get the milk for free ~

whoever said that first can answer your question.

Possibly because respecting the woman that you're with and having genuine feelings for her brings you pleasures beyond the realm of fulfillment of sexual desires? Iunno.

U can fuck someone & not like them, so I can say its normal, but not healthy.. not judgemental.. I did that too once..hold ya head