Two, one I just met for the first time in five months, the other is pretty new so I don't know yet.
I wouldn't let the posts here make you paranoid. I think there are just as many exclusive affairs on here. I only have LDAPs and currently define the both as FWBs so that means there is neither the emotional depth nor the frequency of dates that I would need to want to be exclusive.
If a guy keeps me satisfied emotionally and physically, I'm much less likely to have others, and when I'm in love... they all disappear (though right now I think it's smarter to NOT put all your eggs in one basket). So I'd say a lot depends on the quality of your relationship and how happy she is with you and what you have.