Many timeshare systems impose a minimum stay upon their members. The rationale is typically reduced cost--minimum stays result in fewer total reservations which equates to fewer bookings, fewer check-ins, fewer housekeeping visits, etc.
Although Disney Vacation Club does not currently impose a minimum stay, the Public Offering Statement does give them the right to institute a minimum in the future.
Topic: How would a 5-night minimum stay change your attitude toward the DVC program?