Make it a point to do a quick check everyday.
I booked our reservations last year and have been checking and checking.
AAA has consistently been a couple of dollars over the supersaver rate with no fluctuations and AP rates have been listed as unavailable.
Last week, only 3 weeks out from our trip, AAA rates significantly lower than Supersaver and really good APH rates showed up for 1 day. I quickly changed to AAA from Supersaver.
The next day, the rates were gone again.
So, lesson learned - check every morning and grab it quickly if they show up.