With a December Use Year:
your '06 UY points are valid for stays from Dec 1, 2006 - Nov 30, 2007
your '07 UY points are valid for stays from Dec 1, 2007 - Nov 30, 2008
your '08 UY points are valid for stays from Dec 1, 2008 - Nov 30, 2009
If you want to book at stay for Oct '07, that falls within your 2006 Use Year so you can use any of the following points to "pay" for that stay: banked '05 points, '06 points, borrowed '07 points.
You can always book at your home resort 11 months prior to your checkout date regardless of your Use Year, and 7 months prior at non-home resorts. You just need to have enough points available in the same Use Year as your vacation dates.
Hope that helps!