I have two (equal) partners and one FWB that I see about once a month. I'm almost at my saturation point. I used to have three serious partners and back then I was definitely saturated. So maybe either two serious partners and two FWBs or three serious partners is my upper limit. But then again, it all depends how often you see them and how much you keep in contact.
I've been thinking about this subject recently, because I have a person in my life that I seem to be developing something with, but I don't think it can be anything more than FWB at the moment. I'm really weighing my capacity and whether it would be wise to start anything right now. But in the end I don't think I can really plan it, so we'll just see what happens.
Me: bi female in my 30's
Partners: Hank, Dahlia and Fay
Metamours: Eddie (Dahlia's long-term partner)
Living with Hank, Dahlia, Eddie and rory (my ex/friend)