What is often the point of confusion is that members try to think through the situation based on date they are calling to reserve. Simplest way to look at it is to ignore date you call to reserve, look only at dates you will be at WDW, and whatever use year those dates fall within will be your "current" use year for that trip. Then work off of that to determine whether you need to bank from the "prior" use year or need to borrow from the "subsequent" use year.