These folks will make you a Platinum member in their SPC program if you're already one with Marriott, with little or no hassle, just send them an email asking and it happens almost immediately. Renwewal requirements are fairly simple as well.
Starwood comps you through the end of the calendar year and then no more unless -- You maintain the level with 25 eligible stays or 50 eligible nights each year. This minimum requirement is based upon a calendar year, January 1 through December 31. Less than 75 nights, for sure.