What does that have to do with your dignity? If he's only sticking around for sex, you might end up wasting months on a loser. There's not much dignity in that. If the drop you like a hot potato, at least you can kick him to the curb before you get your heart involved.
I think you missed the point, Beks. If you give a guy sex when you have only been a date or two, and he dumps you, you can be left feeling used and tossed aside. This is assuming you were looking for more than sex. Generally, a guy who just wants to get laid won't hang around after the first three dates if all he's interested in is sex. If he books it and you didn't sleep him, then at least you don't have to regret sleeping with him or worry about what little "presents" he left behind. I gather that in newborn's case this is an international long distance relationship, which throws a whole new factor into the deal.
Losers don't usually wait around for sex for months.