Umm...

[nettiesaur]

I think those at those venues where there is high demand, those front rows go rather quickly. This might happen at the first few shows of the tour, whichever one they are recording, the shows on weekends, Madison Square Garden, etc.
I was dreaming about maybe going to the Phoenix show, and looked at tickets online for quite a while before realizing I couldn't do it. However, there were still floor seats available for weeks after they went on sale. I think it really depends on which show you are going to and what the demand for it is.