From the correspondence that I get, I find that there is a perception that a man who is cheating on his wife will stop having sex with her. I sometimes get letters from "the other woman" asking me if she should believe a husband who claims that he isn't being intimate with his wife anymore. I'm not sure why, but this is often very important to her. She might say: "the guy that I have been seeing has told me that he didn't sleep with his wife for six months before he met me and that he hasn't been sleeping with her since we got together. They have kids, which is the only reason he stays. However, I have a friend who is also friends with his wife. And she says that she would not be surprised if they are still having sex because they both act normally and somewhat affectionately when they are together. She said she just saw them holding hands walking around the neighborhood. Could he by lying to me?"
Along that same line of thinking, a wife might suspect her husband of cheating but ultimately may decide that he probably is not because their sex life is still active and still pretty good. She might assume that because the husband is getting good and frequent sex at home, then she has nothing to worry about in the infidelity department. She might say: "my husband has been away from home much more than usual lately. He works late. He goes out. He takes more phone calls than usual and takes them where I can't hear what he is saying. I would suspect him of cheating except for the fact that we are still having some pretty good sex."
From my observation and experience, these assumptions are not always correct. Many men who have affairs do continue to have sex with their wives without anything changing or seeming to be amiss. In fact, sometimes the sex is more frequent or even better while he is having the affair. He can do this as to not arouse suspicion or he can do it because he is still invested in his marriage and still very attracted to his wife.
In fact, it's my opinion that most men never did have any intention of leaving their wife and still do not while the affair is active. So for them, nothing is going to change. And because of this, there's no reason to stop having sex. Sure, they very convincingly tell the other woman that they want to or are going to leave. They will tell her that they are married in name only and that they haven't been intimate in years. They tell her these things even when they are not true because they want to make it easier for her to cheat. They don't want for her to identify with the wife or to realize that she's in a relationship with no real future.
Frankly, it is not fair to the other woman. It is lies that are being told to her. But this scenario is very common and many "other women" eventually put two and two together and realize that they are being lied to. And many wives eventually find evidence of the cheating and have to face reality even when their sex life still appears to be active and wonderful.
So the answer to the question is that yes, man very often continue having meaningful and good sex with their spouses while they are actively having an affair. It is wrong. And it confuses matters. And often, the wife and the other woman do not understand this because women are less likely to be able to comprehend how you can be having sex with two people.
I really don't have a definitive answer about this because I could not carry this out either. When I love someone, I could never be unfaithful. But obviously, as a woman, I do not think and act like a man. From the correspondence that I get, it seems pretty clear, at least to me, that men are much better at being about to separate the two relationships and compartmentalize their feelings and their thoughts. If I were the one having an affair, I would be so crippled by conflict and guilt, but some men are able to juggle it pretty convincingly.
Again, this is only my opinion, but if I were dating a married man and he told me he wasn't having sex with his wife, I would have serious doubts about this. From my observation, most of the time, this just is not true. Two people under one roof and in one bed with a shared commitment are most likely having sex. Many men tell the other woman they sleep on the couch or spare bedroom. This often isn't true, either.
And many wives want to believe that as long as she's having sex with him, then he doesn't need to seek it elsewhere. The truth is, he is getting a different pay off from this than just sex. He is often using the affair as a way to feel better about himself. Sex often has much less to do with it than people think.
My husband and I were separated by distance when he had has affair because of work obligations. However, our relationship at that time was good and active. He cheated for different reasons. I outline some of those reasons on my blog at http://surviving-the-affair.com