I told myself I wouldn't do this but....
There are two booking windows: you can book a stay at your "home resort" (the resort where you own points) from the current date (today) until 11 months out (for example, I can book a stay today at my home resorts, Boulder Ridge and Saratoga, starting as far out as December 11th of this year).
You can book at other resorts (where you don't own any points) from today to as far out as 7 months (I can book at Beach Club, a resort that I don't own at, for any days from today until June 11th, pending availability). No one, under any scenario, can book any trip that starts AFTER December 11th of this year. Before the 11 month window, you can book as long as you like at your home resort, and before 7 months you can book at another non-home resort (for as long as you like).
There are exceptions regarding Riviera, but that is an outlier currently and the basic 7/11 month rule applies to the vast majority of situations. It's BEYOND 11 months that you can't do anything.
If I DO decide to book that home resort trip at 11 months, I can only book a total of 7 continuous days initially. If I book those seven days today, I can log back on tomorrow and add another day on to the end of the reservation and continue to do so daily, up until I reach 30 days or run out of points.