From my point of view it's difficult to understand why you would go there. My point of view.. not saying it's right. I can see it becoming a problem later down the track when you meet the guy you want to marry. You'll be introducing him to your best friends who you've slept with, and you can't fall back on the "we're just friends". I've always been skeptical of the "just friends" line, because it so often fails. I also find it interesting that the men were also willing to sleep with you. This validates my view that for the most part, males that keep female "friends" around I would say more often than not plan to sleep with them. They're the White Knights that wait for the opportune moment, whether it be a breakup or a drunken weekend, they're there as a shoulder to lean on more-so as an investment into future sexual encounters. They're the stubborn one's that hold on regardless of the "friend-zone". If it were me and I truly valued the friendship above sexual gratification, I'd politely refuse.
It just seems odd to me that their motives would be anything other, given their willingness to go there. They were waiting. See it so often. I think they're sickly predators.