Preexisting relationships will definitely be harder to turn into a polyamorous one than a couple that started out with polyamorous intentions. It’s a nice existentialist thought where a person could have a variety of constant intimate options with enough variety to keep things interesting but enough consistency to give you emotional stability. At least that’s how I always think of it. But to actually execute it would definitely involve a lot of work. One relationship is a lot of work so to invest in that many committed relationships at the same time sounds more like a hardship than freedom. But, I think it is a great way of living in long-term, nonetheless, because as long as everyone involved are on the same page where communication is the absolutely necessary adhesive to make this work, it sounds a lot better than marrying someone, getting a divorce, finding someone else, and repeating.