Me personally: antything beyond 3 dates starts to look suspicious.
1. She is stringing me along for a reason I do not know - I lose interest.
2. She has low self esteem - tries to build her value by making me wait, in accordance with the principle that whatever you work for to attain, you value. She backwards rationalises that if she wants me to value her (casue she doesn't herself) she needs to "make me work/wait" for it. I lose interest...
All my long-term relationships started with sex happening relatively quickly...
As my friend put it, "if a woman meets the man's relationship criteria, then whether she puts out on the first date or the tenth, is irrelevant. If she doesn't do so soon enough, the guy reckons she isn't interested and bails."