I was hesitating to chime in, despite being the hinge in a V with two partners who are not dating anyone else because I did not open my marriage to poly. We were poly from day one, with members of our extended polycule standing up with us as part of the wedding party. My NP/husband, MonkeyMan, self-identifies as poly but considers his plate full with one relationship, one career, and being a dad. My long distance boyfriend, RacingSnail, identifies as mono... but only because he recognizes that his plate is full with one relationship, similarly. Neither of them needed any ‘convincing’, though RacingSnail and I do periodically trip over some unexamined mono-normativity that one or both of us has absorbed from the dominant culture and have to explicitly challenge. Anyway, fwiw, there’s my 2¢.