Pay attention to post #23 from Marriott Concierge in the thread at the link I provided in my previous post. You need to drop to Gold (March 1, 2010 if they don't renew you at Plat) before you can use the rolling 12 months to once again attain Plat. So hopefully most of last year's stays were in the last 10 months, and your drop to Gold will be short lived.