And you think this has to do with your time period for having sex with them and not some other compatibility measure?
Here is a honest break-down for you and bofa, you don"t get to force a girl into wanting more than a temporary sexual relationship by putting it off in the beginning. You can make her want you more, for sure, but it"s not going to translate into some over-arching true love scenario just cause you pull it off. And while you can pull it off if you aren"t really good at it, you"ll fuck it up just as easily. Take some when you can get it, I say. You probably need the practice more than you need to make sure this girl becomes "the one."