That's why I mentioned the importance of being able to book in advance. With few exceptions (VGF comes to mind) you can generally book at 11 months out at your room resort easily. However, if you buy based on certain categories then you are bound to be disappointed at times. For example, if you buy at AKV with the plan to always book value rooms, you will likely often be disappointed they aren't available. However, standard and savannah view rooms are almost always available for several months after the 11 month window opens. Likewise, if you own at Boardwalk, you may find that the standard (low point) rooms are gone very quickly at 11 months during popular seasons (Food and Wine), but even this resort is frequently available for Pool/Garden rooms 8-9 months prior to booking.
Where the competition REALLY heats up is when the 7 month window opens up. While many resorts still have availability right when the window opens, they will frequently book up in the next few days. If one of these tables shows a resort as "Open" at 8 months and "Spotty" or "None" at 7 months, you can bet that's a resort that gets filled up very close to the 7 month mark.
If you can afford enough points to book 1-bedrooms, these rooms have a much longer availability. Of course, they cost twice as much as well. These haven't really been tabulated here too extensively, but a good example here is to look at Wilderness Lodge villas, and the difference between the studio and 1-bedroom tables.
Of course, what cannot be accounted for here is the exact dates someone wishes, nor the use of waitlists. Many people say waitlists have worked very well for them.
We've only been members for 3 years, but we have had no issues with booking, but we know when it is busy, we just book our home resort, and if it is slower times we plan on moving right at 7 months.