If you call and "pose" as an annual passholder, you can ask for AP4 rates for the given time period. you would have to have an AP in hand in order to check in at that rate though.
I upgraded last time I was in DL partly so I could take advantage of these rates, but alas did not know where to look on the website for them until they were almost sold out. I was able to get a Park View room in the PPH for 149/night for 9 consecutive nights in December. Last May, I could only book mid-week at regular prices - about twice that rate.
The special rates are for 9/3-9/18 and 11/14-12/15 only (Thanksgiving is black-out). Like I said mostly sold out but PPH is still available at special rates for December. IMO worth upgrading for the rate if it's what you want, but you have to be on the ball as to when the rates are released.
Hope that helps - you would be able to get all the info you need with an annual pass in hand since you could then log into the website.