I feel your pain, we closed a couple weeks ago and I asked our "guide" repeatedly how many issues we would have booking the 7 month window, of course the answer was no problems at all. Now almost all of the resorts are free except for a couple of days. I am always asking myself how a hotel gets totally booked one random wednesday during the week ;-)
One thing to remember - DVC is a timeshare, not a hotel. They sold enough points for the resorts to be fully occupied all the time - except for maintenance. If any room is available the day of, it means someone isn't using their points.
Members come and go at all points during the week. A lot of members use DVC for partial weeks or a night or two in addition to a cruise, so if the cruise leaves on Saturday and returns Wednesday, they book Friday night, then Wednesday through Friday when they return. Or in addition to a stay at Universal, or a visit to the beach, or a stay at Grandmas.
When the system is working at capacity, at 11 months every room is available. The day you check in, no rooms are left (well, one or two might be held for maintenance so if a toilet breaks....). Very often there ARE rooms available last minute - members cancel, they don't use their points and few points expire - but that is your fellow members not using their points - not Disney having more capacity than they sold. At what pace you go from 100% available to 100% booked depends on the time of year, the resort and the room type.