Understanding Use Year -
Use year is the month your points are renewed each year. You have one year to use the points before they expire unless you bank them.
Use year determines your banking deadlines, but it has nothing to do with when you can make a reservation. You can always call 11 months prior to check out for a reservation at your home resort and 7 months prior to check out if you want to reserve something at a non-home resort.
Let's say you get October for your use year. Let's say you decide to buy 200 points.
On October 1, 2006 you would get 200 points to use for stays between 10/1/2006 and 9/30/2007. Those would be considered your current use year points for the 2006 use year and any stays that occur during that time period. (If you buy now from Disney and get an October use year, you also get 2005 use year points with your purchase).
If you don't plan a trip before 9/30/2007, you'll want to bank your 2006 points so that they do not expire. As long as you call before the end of March 2007 (the 100% banking deadline), you can bank all 200 points. If you wait until the end of June 2007 (the 50% deadline), you can only bank 100 points. If you wait until the end of July 2007 (25% deadline), you can only bank 50 points. You may not bank at all in August and September if you have an October use year.
Your 2005 use year points are good for stays between 10/1/2005 and 9/30/2006.
Your 2006 use year points are good for stays between 10/1/2006 and 9/30/2007.
Your 2007 use year points are good for stays between 10/1/2007 and 9/30/2008.
Your 2008 use year points are good for stays between 10/1/2008 and 9/30/2009.
etc.
You may bank points one use year ahead and borrow from one use year ahead.
Let's say you want to stay in May of 2008 and your stay will cost 500 points. May, 2008 falls within your 2007 use year. For that reservation, you may use current use year points from the 2007 use year, any banked points originally from your 2006 use year and you may borrow points from your 2008 use year.
Banking and borrowing are final transactions. If you cancel a reservation made with banked or borrowed points, they cannot be returned to their original use year. So they would expire at the end of the current use year unless they were used before then. You may not bank or borrow the same points more than once.
Let's say you have to cancel that May, 2008 vacation. You call to cancel it in March, 2008. To make that reservation, you used 200 current use year points, 200 banked points (from 2006) and borrowed 100 points from 2008.
After you cancel, you would have 300 points to use or lose before the end of your current use year (9/30/2008) - the 200 that were banked and the 100 that were borrowed.
If you called before the end of March, 2008, you could bank all 200 of your 2007 use year points. Now those points are good for stays between 10/1/2008 and 9/30/2009. They expire on 9/30/2009 if not used before then - you cannot bank the same points more than once.
ADVICE: If you travel about the same time of the year on a regular basis, it's best to choose a use year that falls no more than 4 or 5 months prior to that time.
Use year only matters if you have to cancel a vacation that was scheduled to occur late in your use year - because banking is limited late in the use year and you wouldn't have much time to reschedule before the points expire). Many owners never have to cancel a vacation (lucky them, LOL) so they don't worry about use year. Remember, use year has nothing to do with when you may call to make a reservation.
Keep in mind that your travel pattern may change over the course of your ownership. What starts out as a "perfect" use year may end up to be not so perfect.
Hope all that helps you understand how use year works.
Best wishes -