I'm probably the last person to ask, but your question did strike me as a little "funny"/strange in that you talked about time intervals (two months) and number of dates. I guess I never thought in those terms when dating, believe it or not. I get the feeling that that is more of a "girl" thing than a "guy" thing.
I guess my feeling is that whether you have sex with someone would depend more on mutual feelings, whether you have discussed the nature of the relationship you each want, whether you have discussed birth control, whether you have discussed and gotten commitments on exclusivity (if appropriate), etc. I don't think there is any set schedule for those sorts of things.
I think I have told the story about my relationship with my exGF. At one point she said: "It was 22 dates before you kissed me!" That's true, I suppose. But part of the reason for that is that she was counting the dates, and I was not.
Part of the reason was that she was so talkative, she succeeded in convincing me that she was a lonely woman who just wanted companionship and someone to talk to. Fortunately, that was a misunderstanding on my part.