What is referred to as "use year" controls when you get annual allotment of points, by when you have to use them, and by when you need to bank if you want to bank points from one use year to the next so you can use them in the next use year. It does not control when you can go, which is any time of year, or when you can call to reserve, which is always up to 11 months in advance at home resort, 7 at others. By example:
1. Assume you have a February use year.
2. That means each year you will have an annual allotment of points in your account on February 1, and they can be used for a trip that begins and ends between Feb 1 and Jan 31 of the next year, unless they are banked.
3. Assume you owned today, have an annual allotment of points coming in Feb 09 and you want to go to WDW at your home resort in August 09. You can call in Sep 08, 11 months in advance at home resort, and reserve that Aug 09 trip using points to be issued Feb 09.
4. Now assume you have Feb 09 points coming, but you do not intend to go until March 2010. You have all those Feb 09 points coming that you won't use by Jan 31, 2010, the end of your 09 use year. If you do nothing you lose them. However, on or before the end of your eighth month in the use year, you can bank any or all of those points into the next use year, meaning on or before Sep 30, 2009, you can bank those points issued in Feb 09 into the Feb 2010 use year. Thus, for the Feb 2010 use year you would have both your banked Feb 09 allotment and new points coming in Feb 2010, and you can reserve that March 2010 trip (by calling in April 2009) at home resort and make it extra long because you have a double allotment of points to use.
5. You can also "borrow" points from a use year. Assume again you want to go Aug 2010 but you call today to reserve and you want to use 200 points but you have only 160 coming in Feb 09 to use. Needing 40, more you borrow those 40 at time of making ressie from the 2010 use year, so you can make that Aug 09 trip using all your Feb 09 points and 40 points from Feb 2010; of course, in that case come a trip to be taken during the Feb 2010 use year, you will have fewer points than your full annual allotment to use because you have borrowed some for use in 09.
6. Banking and borrowing cannot be undone. If you bank points, they stay banked into the next use year and cannot be brought back. If you borrow points, they stay borrowed into the earlier use year and cannot be sent back. Banked points must be used during the use year into which they have been banked as they cannot be banked a second time.
7. As to "desirable" use years, it usually makes little difference (also, there are no Jan, May, July or Nov use years). However, there is the issue of the "cancellation/banking hedge." This applies if you actually intend to go about the same time every year. If you cancel a trip more than 30 days before arrival, all your points go back into your account as is -- regular points go back as regular points, banked as banked and borrowed as borrowed. The banking hedge is explained in the next example:
8. Assume that Feb use year and you make a trip for April 09 using Feb 09 points. Come Feb 09 you have to cancel. Points go back into account and you still have a year to use them and plenty of time to bank them. Now assume instead you reserve a trip for Dec 09 using those Feb 09 points and come Oct 09 you have to cancel. All those points go back into your account but because it is Oct 09, you are beyond the last banking date and cannot bank them into 2010 and must use them for a trip that ends by Jan 31, 2010 or lose them. To obtain the cancellation/banking hedge to avoid that situation, many recommend that you get a use year that begins shortly before you usually go (actually any that begins up to eight months before you usually go preserves the hedge). In other words, if you usually go in Dec, you likely want to avoid a Feb and March use year to assure that if you cancel you can still bank points. If you usually go in Dec, ideal use years are Dec, Oct, Sep, Aug, and even June or April are fine. At the same time, don't over think the banking hedge because your regular time for going now may change radically in 10 years.