As with everything in polyamory, it's up to the participants to decide. When James and I first started out, he didn't interact with the other man if we were with one, but a couple of years ago we met someone that he wanted to be intimate with and so he did. It's really just whatever works for you (all of you). I enjoy being the focus of two men, but find that is still to a large extent the case even if they are also intimate.