I do have two partners in addition to my primary relationship, one of whom I see four weekends a year. The local one has a busy life and small children and we will probably be lucky to arrange sexual intimacy together twice a month in the future, although it's hard to tell since we're very new. I also don't have any issues that get in the way of having sex, and I can meet the sexual needs of any of my partners with enthusiasm, no problems at all.
My primary partner's promise wasn't "empty," and I don't know where you got that idea. It was an agreement we made with the enthusiastic support of our sex therapist, who thought that one new lover at a time made a lot of sense for him considering his physical and mental issues and things we've weathered as a couple. Now I just have to decide whether I'm going to hold him to that. I didn't expect that R would ever be interested in dating him again, I thought they were over.