A few years ago our trip spanned late sept/early oct, and the crowds were really high. They ended up extending park hours each day while we were there, but didn't announce it until about 5:00 pm each evening. When I asked on the first day, a cm said they are making the call based off of each days attendance.
I am glad that they can do this on an as needed basis, however, I too would think they could be more intuitive with their park attendance estimations and plan accordingly. Knowing the trend the Fall season has taken the past few years with the ramped up Halloween decorations and ride overlays as well as Halloween parties. Disney has done all this to bring in crowds, and it's working, yet they are not keeping up with it in terms of hours and entertainment.