From what I can percieve, waiting has become a thing of the past. Second date, third date, a month?
My short answer is 6 months

However, Roadius Ragemorpheus, has a better idea. The wait is not determined by time but by knowledge. Sort of like that Eharmony concept of compatibility on 29 dimensions. And I think that is based on something like a 500 question inquiry.
In my opinion, it takes a time and communication for two people to really get to know each other. Seldom does current norms for sex revolve around depth of understanding but rather the degree of lust.
It is a mistake to become sexual very quickly in a relationship. Of course, you would have to be an old geezer to understand that. People are mostly operating today without the benefit of wisdom and actually scoff at it.