Well, me and 3 are no longer FWBs.
I've managed to put that down to three main things:
1. We were not sexually compatible
We talked a lot before we agreed to become FWBs and we realised were super compatible on paper. It turns out that being compatible on paper doesn't mean you're compatible in real life. And hell, we were even compatible all the way through third base. But the sex itself was dismal. It wasn't anyone's fault - it just didn't work out.
2. He did not want me as much as I wanted him
This part really is the sticking point. I pursued the guy for two months - he eventually came around. I wasn't terribly physically attracted to him, but that isn't something that matters to me. On the other hand, he BARELY found me attractive. I have short hair; he hates short hair. I was on the verge of being too fat for him (I'm 5'8", 70kg, so it was a reflection on his love for skinny girls than my size). If we were to have sex, I had to be the proactive one. I had to schedule an evening, make sure it fit in with him, and all the rest of it.
Mr Wonderful, on the other hand, is more than happy to go to bed with me whenever I want and makes passes at me with pleasing regularity. This contrast, not to mention my better sexual compatibility with Mr Wonderful, really opened my eyes to how things with 3 would be going if we actually should have been FWBs in the first place.
3. We liked the idea of being FWBs more than any other aspect of the arrangement
This is more the answer to "why didn't it end earlier?". We liked the idea of having FWBs. We liked the list of rules I linked to in an earlier post. We liked the attention. We especially liked being able to talk about it in front of other people and make them uncomfortable. But that's a stupid reason to continue a sexual relationship with someone.
Oh, and I was about as bad a person as it was possible to be in the way I ended it. I like to think I did it that way to put a wedge in between us that would prevent us from changing our minds; but in all honesty it was really because I'm a bitter person.