My fuckbuddy is like you, his wife lost all interest in sex. He however still loves and wants to be with her and his family and I have no desire to be in personal realtionship with him. So naturally I provide for him, a healthy, comfortable and easy sexual outlet for him. We are both happy and satisfied with this arrangment and neither of us having any romantic or personal feelings towards one another. Its purely a carnal relationship, which is why I think we work so well.
I can tell there are times when he does miss the sex with his wife or a woman, because occasionally the MM sex we have, will be very "passionate" and more "love making", then usual depraved acts we enjoy and engage with. I actually enjoy the "love making" when it occasionally happens, as a point of difference. He will spend a lot of time kissing me, rimming me and sucking on me from head to toe, he is a lot more caring and loving in the way he treats my body. My hole is literally soaking from his saliva before he puts his dick inside me. Its careful, considerate and thoughtful. So naturally I adjust myself to his tempo and make sure Im a lot more feminine, caring and loving with him in response. The anal sex positions we engage with during these "love making" moments are only either spooning, suspended congress and of course missionary. He will always cum when we are in the missionary position and no other. He enjoys seeing me get off on being fucked, its about the only time when he is very considerate and careful when he fucks me. As I said, I prefer the depraved acts we have, but also love the "love making" just because its something different and spices up our sex life. The biggest telltale sign I can tell immediately of whether we have depraved sex or love making, is the moment we meet up. If he starts kissing me passionately the moment I enter the door its always been a "romantic/love making" encounter ahead for us.