According to the TOS, MM4 is employee only and should technically only be valid during the holiday season. It would depend how lax the FD agent is on collecting the form/checking as every person/property is different and I can only recall only once not being asked to show it. It does appear that Marriott might have gotten stricter as the forms USE to be valid for the calendar year and now has an expiration date of about 3 months. Do you risk using MM4 and being denied the rate or go with the higher MMP rate and getting a room? Your call.