Use year has nothing to do with when you can go (any time of year) or when you can call to reserve (11 months out at home resort, 7 at others).
It does set the date by which you must bank your points into the next year if you want to bank. Currently, that date is the end of the eighth month of your use year, e.g., if you have a September use year (runs Sep 1 to August 31), you must bank by April 30 in any given use year. You cannot bank any points during the last four months. The use year thus becomes important only in the situation where you set a vacation and then have to cancel. Assume that Sep use year and you schedule a trip for July during the use year. Now assume you have to cancel come May. Points go back into your account but you cannot bank any of them because you are beyond the last banking date and thus points must be used for a trip that ends by Aug 31 of the use year or they will be lost. Assume that Sep use year and you reserve a trip for Dec. In Oct you have to cancel. Now the points go back into your account and you have plenty of time to use them or bank them.
Thus, if you actually have a usual time of year that you will go, many recommend that you get a use year that will allow you to bank points if you have to cancel. For example, you say you would usually go between October and December but might also want Jan or Feb. Use years to preserve the banking/cancellation hedge for all those months are Oct, Sep, Aug, or June (there is no July use year).