I currently have...7 going on, with seven different partners. All radically different stories. I've had up to 12 at a given time. 12 might have been too much.

I'm mostly here because I love to write, and I write a lot. I know there's a quantity over quality thing, but I try to never let it get in the way. This results in my sometimes super glacial responding (I'll usually get out 1-2 responses every day or so to a partner but it gets up to the point where it's been four days and someone has to poke me). But also because of the time difference between me and most of my partners (who live in America), I get an entire workday to do work and then I come home and respond to them when I have literally nothing else to do.

I assume my partners know that I'm not just talking to them. I don't know why they would expect that unless there was an agreement. I agree that there's no unspoken rule about monogamy here. Privacy, sure. I wouldn't tell my partners who I'm writing with, or what it's about, but I will say things like, "I have to send a response to someone else but you're next up!" or of the like.

I like the creativity that comes along with having multiple scenes going on at once. It forces me to switch gears (and tenses and POVs which really challenges me). I don't think I could ever write multiple stories with the same person (it'd get too confusing and be too hard to not let the characters bleed into one another).

Also different people bring different ideas to the table. If your partner posted the exact same prompt, perhaps she wanted to explore it with you but also wanted to explore it in a completely different direction or with a completely different starting point. That's what's so great about this place, there's no end to where a situation can take you.