I agree with constlady. Taking the time to develop each relationship is key. I also agree that for me two primaries and a couple of tersiarys is more than enough.
I was trying to juggle a husband, a male OSO (Mono), a tersiary woman and two tersiary men at one point and be an attentive mother. It was far to much.
What it meant was no one got quality time with me and most of all I had no time to attend to my own time. I still struggle with that last one and I have two less now in my life.
The thing with having NRE about poly or what some people call limerence is that it makes us feel un-stoppable and on top of the world. It works out fine to have many relationships at once when the realationships are new because the depth isn't there yet. Trouble is that eventually the next level of relationships is to work on depth and that is when its hard not to be spread too thin.
In my circumstance I found that I had to drop a couple of people (one man and the woman) in order to make way for depth with the three left. I don't regret dropping them at all, but it was hard to say to them that I couldn't spend time with them because I wanted depth with others. I am still friends with the woman and the man and I are still negotiating speaking terms. I would of avoided all that by not jumping into sexual and intimate relationships with them both from early on. My version of poly was different from theirs too and I wished I had negotiated all that before getting invovled with them.
Thankfully there was another man at the time that I didn't become intimately involved with and he ended up being the closest to me in the end. We don't have a sexual relationship, but our friendship depth is deeper because I didn't sleep with him and decided at the last minute to take it slower and work on the relationships I had.
Enjoy your time my friend
you are in an exciting time. Keep your eye on what you want out of it, because in no time at all it will all die down and you will be sorting out who stays and who goes. Give a lot of thought and time to everyone concerned and draw it out as much as you can in order to make the right choice. This is what I wished I had done. It worked out well for me in the end however as I have just what I need and just as much as I can handle.