You basically want a use year of the month you will travel or one of the months right before. If you have June UY and book an August trip and then cancel that trip in say, May, you will still have time to bank the points in case you cannot reschedule the trip for within that UY. Honestly, UY isn't a big thing. My only suggestion/tip for UY is if you buy multiple contracts is to stick with the same UY.