Art, while that may be true, in the art of seduction, you need to have a purpose, a goal and an end mark. Or else it is just a good conversation among the myriad of conversations she will have in her lifetime that she may or may not remember.
Just like in sales, you can talk up a storm and get the prospect engaged, but if you don't close, it's all for naught, you make no money. In the art of seduction, you get no girl. And he who hesitates, masturbates. No one is going to remember you for your good conversation if you don't close or at least progress closer towards your goal.
Like every wave a surfer rides, the wave won't last forever and at some point it is going to break. A good conversation can only last so long before it comes to an end, during which it has to serve a purpose.
One of the universal methods taught in the art of seduction is to cut out early at the height of the conversation. As an artist, you heard the saying "The height of excitement is at the peak of anticipation"? When you cut out, it leaves the girl wanting more and thinking about you. Moreover, you save your vocal cords and your social energy for another girl.
As demonstrated in the game show Keys to the VIP, the classical approach most guys do is a guy approaches with a high velocity attraction and cuts out and n-closes. You don't want to overstay your welcome and talk and talk and talk. The girl is there to socialize with other people as well. And if by chance, you talk to a girl for 2 hours straight, that's the girl you probably end up marrying :P That's pretty much how normal non-PUA guys end up with their gfs.
In texting, that purpose is to move the interaction to 1st tier communication. D1. So in hubert's case, if the girl's response time is slowing down, that means the wave is breaking. Unless, he is a master texter who can charm women through a wall of text, he can't overstay his welcome. He needs to escalate.
@Hubert - For text game, I recommend you get Bobby Rio's "Magnetic Messaging" and Christian Hudson's "How2TxtHer"