Some great points brought up already.
Here's my take on this - ok, so your ideal is to be in a live-in arrangement with someone, and then have other lovers, but what you are asking here (as I understand it) is whether you should have secondary relationships while you are waiting for that person to come along.
Well, two points - first, if they are going to give you an increase in your happiness and help you learn more about yourself, then why not?
Second, since you self-identify as poly, presumably you would want to carry that on even after you have found a live-in mate - so that wouldn't necessarily mean calling an end to your secondary relationships, right? (Presumably these people aren't wanting you to be a secondary to them and have no other relationships - that's kind of unrealistic on their part, if you are not happy with that).
"Listen, or your tongue will make you deaf." - Native American Proverb