We have a prime golf week and have used it for off season Westin in Hawaii.
The trouble with exchanging to Westin and Mariott is that owners get first crack at availability. I think it's 30 days?
The leftovers are available to everyone.
I own 2 SDO eoy weeks in order to take advantage of that exclusive period.
If you are thinking of buying a Sunchaser week in order to trade into Hawaii in high season, don't.
You would be much better off to buy an SDO week. Even then you would want to put in a request first, and don't expect to get popular weeks.