IMO, use year is far more important for many members than they realize. It all comes down to what if you have to change your plans or cancel in any way. Anyone who can't travel easily throughout the year and do so without having to plan long in advance can likely do well with any use year. Those limited to certain travel periods and/or would have great trouble using points if they had to cancel, should pay more attention to their use year choices. But there are a number of factors, esp going resale. One must consider the home resort, price and points accounting. Is it worth passing up the right resale simply because of use year, generally not, but for come they should consider it.
IMO, the best use year is one that occurs within 6 months ahead of all your usual travel periods. Say you normally go in June and Dec, Dec would be best and June second. The more time you have in your use year AFTER your usual trips, the better off you are.