All awards are subject to availability, and PointSavers are even more restricted - typically only available during off season demand periods.

http://www.marriott.com/rewards/marr...PointSavers.mi lists the available properties/periods, and notes that their are new deals every week. Right now is only shows 17 US properties, each for only 1 to 3 week periods, or specific Sunday and Thursday nights, etc..