Take a look at the "How do you know you're poly?" thread. I think it will give you some insight on this question.
From what I can tell there are:
-People that are innately poly and need a poly lifestyle to be happy.
-People that are innately poly but do not need a poly lifestyle to be happy.
-People that are innately mono but do not need a mono lifestyle to be happy.
-People that are innately mono and need a mono lifestyle to be happy.
Obviously this is way oversimplified and it is much more of a spectrum. There are people on this forum all over the spectrum. There are also of course lots of different styles of what constitutes poly. If you take a look at the thread I mentioned we talk about a gradient between mono and poly and also a gradient between swinger and poly. So poly means different things to different people, and you may need to get a "what would this look like on a daily basis?" type of definition worked out before you can really have this discussion.