It goes both ways: As you get closer to the booking time, if the rooms that the third parties have allocated aren't mostly booked, they generally start to drop prices in order to fill the inventory (I'm assuming because they have paid for the rooms in advance), whereas I have never seen a hotel do this directly. I have gotten some great deals from booking last-minute through sites like Agoda where the price was significantly lower than it would have been going through the hotel directly.