The last night for Elf on a Shelf varies depending on the specific tradition followed by different families. In general, the last night for Elf on a Shelf is usually Christmas Eve, when the elves have to go back to the North Pole to report back to Santa Claus. However, some families choose to have their elf stay for an extra night, known as "Sleepytime Elf," where the elf remains hidden and resting during the night and reappears in the morning with a note from Santa explaining that the elf needs a little rest before the big day.