Use year is irrelevant to when you can go (any time of year) or when you can call to reserve (always beginning 11 months out at home resort and 7 at others).
Its possible relevance has to do with the combined issues of banking and cancellation. You can bank any or all of your points from one use year into the next for use for a trip in that next use year but you must do so by no later than the end of the eighth month of your use year, e.g., if your use year is February, you have until September 30 of the use year to bank into the next use year; example you have Feb 2010 points, if you bank them by 9/30/10 you can use them for a trip in the Feb 2011 use year (anytime between 2/1/2011 and 1/31/2011).
Now we get to the cancellation issue. Suppose your use year is February and you currently have your Feb 2010 points for use. They must be used for a trip that ends by no later than 1/31/2011 unless you bank them. Now assume you call today and book a trip using those points for the last week of January 2011. Next assume something unforseen happens and in November 2010 you learn you must cancel that trip. You do so and the points go back into your account. However, you can't bank them because November is after your last date to bank, 9/30/10. You thus have only until 1/31/2011 to use them or you will lose them.
Now a different assumption using the same Feb use year. You call today and use points to be issued 2/1/11 for a trip at the end of Feb 2011. That trip will be in your 2011 use year and thus those points issued 2/1/2011 will be your current use year points for that trip. Come December 2010 you have to cancel and points go back into your account. However, you now have until 1/31/12 to use them or you have until 9/30/11 to bank them into the 2012 year. In essence, no issue of losing them if you have to cancel.
As a result, many recommend that if you have a regular time of year during which you will go, you should get a use year that starts shortly before the usual time of year you go. In reality, to avoid the issue of being unable to bank if you have to cancel, you can actually get any use year that begins up to 8 months before the time you usually go but better to be somewhat closer than that, e.g., 0 to 4 months. Note, I use 0 months because if you usually go in Feb then Feb is an ideal use year because your points begin 2/1 and thus any trip in Feb would be using newly issued points.
Just note, however, that what is good now may not be as good later. For example, someone who goes every year in July to fit kids' schedules may in 15 years when kids are grown start going every year in January. Moreover, the issue makes little difference if your current probability is to go at varying times of year.