you can book at your home resort at 11mo and at all other
DVC resorts at 7 months.
Lets say your membership is 250 points at BWV.
You want a reservation for the July 1 - 7, 2002.
You could make a reservation at BWV for this week on Aug 7, 2001 (11 months out). You could make a reservation at OKW, HHI, VB or VWL for this week on Jan 7, 2002 (7 months out).
Exchanges outside the DVC resorts are treated like home resort reservations.
Now if you have points in multiple resorts, it get tricky.
The points must be used based on where they are at. Example: you have 150 points at BWV and 50 points at OKW. You want to make a reservation at BWV that will require 180 points. You will only be able to use the 11 month window at BWV for those nights needing upto 150 points, the remaining nights will have to be booked at the 7 month window.
Hope this is clearer than mud