Well, the last time I looked at the AP Calendar, just a few days ago, there were rooms available at both the DLH and PPH in September - quite a few, in fact. So here is what I am thinking - OP, if you do not have an AP, then probably the regular rooms available through Central reservations are booked, but there are other ones that are blocked for AP holders and those are still free (though going quickly). So technically, there is availability, but different rooms are held for different things. Also, there is a PIN discount offer that some people received (some didn't) for 35% off room prices, and that expires on September 30, so other rooms are blocked for that offer and those may be available too (but you have to receive the offer), but people are trying to take advantage of that before it expires. Then, on top of that, the get 5 for 3 offer is very popular, and that offer ends sometime in late September, like arrival has to be on or before the 25th or 26th, but the reservations have to be made by August, so I would imagine a lot of people without APs and without PIN offers jumped on those rooms, and that is likely another reason why September is full. Plus, the Halloweentime season will begin on September 25th, so I imagine that a lot of people are using their various discounted rooms with the hotel offers mentioned above in those last few days of September to see the Halloween stuff.