If you go to the reservation page for the restaurant you want to book and put in the date it will show the hours for each meal service. For example on a party night BOG shows reservations until 6:15 are available without party tickets. Then there is a second Dinner schedule beginning at 6:20 with the note underneath "Special Ticketed Event" so you would need party tickets for any reservation begiining from that time. The information about needing party tickets is repeated when you continue with the reservation process. The cut off time for the restaurants I checked (CRT, BOG, CP) varied.
The earlier cut off time for non-ticketed reservations is a change from previous years when you could make dining reservations up to 6:55 PM.