Most of the time it's better to match your use years. If you don't, you essentially have to manage two memberships. To use points from both memberships to book one trip, you either have to book part of the trip with one membership and the other part with the other membership (which will mean you'll have to re-check in and get new room keys at the changeover point), or you have to transfer points from one membership to the other, which can only be done on the phone.
Transferred points won't show up online, so you'd need to do all your multi-membership booking on the phone.
About the only time I've heard where it makes sense to have two memberships is if you have two completely different travel patterns where you go to one resort at one time of year and a different resort at another time of year, and you keep the two memberships separate for the two kinds of trips.