One question I have too is, if when we're talking and there's something I let them know I need to have in the relationship, but they counter with we/he can't meet that need all the time, let's say it's I need a date night every week. Does that mean that things are automatically doomed? or are there ways to compromise? I suppose this probably all depends on the people involved, but generally speaking, or possibly in your experiences, are people in poly relationships good at compromising? Personally I am a very understanding girl who's not super needy and really just wants someone to be with/spend time with once a week or so. But I understand that his wife is his primary and they have kids together. So yeah... any other thoughts or advice would be great!
It really depends on if you truly need a date night every week, if you need a date need every week except if something comes up, or just want a date night every week but could accept once every 2 weeks. If you have an actual need that can't be met compromising on it is just going to get you hurt, but if you have a need that's satisfied but your wants have to be compromised a little every now and then you should be able to work something out. For instance instead of your need being a date night every week, your need might really be a date night most weeks with exceptions for anything special that might come up with his wife or kids. Of course you may have an actual need to see him every week in which case you shouldn't compromise on it.
In general I think poly people are good at compromise, just because if you're not than it'd be hard to manage 1 relationship let alone more. It's a skill that's pretty important to being poly so a lot of poly people have worked at it.