Re (from OP
"So just a question ... how many relationships do you have and how many do you think is too many? and why ..."
How many do I have? If you mean current romantic relationships with living persons, I have one.
How many do I think is too many and why? I don't think I could quote a fixed number, because every person, and every relationship, is uniquely different. Some people want more time and attention in each of their relationships than do others.
The same applies to my personal limit (or saturation point). I don't know how many partners I could handle. I'd have to know each actual person, and experience each actual relationship. It boils down to how much of my time and attention each person needs.
Observation has taught me that three-person units (V's and triads) are by far the most common size where poly relationships are concerned. I've seen Z's/quads here and there but they often slough off one person after awhile. On the other hand, I do know of some intimate networks (of five or more people), and at least one or two of them (that I know of) have stayed together for a long time.
I'm drawing the line at Solomon though. 700 wives and 300 concubines is too much for any man.