It definitely shouldn't be a regular thing.
But when I was an intern, we could accept admits up to 6:30 (or the cap), with NF coming in at 7. There was more than one occasion where we'd get a 3-5 patient bolus from the ED between 6 and 6:30. Then you have to go see them all, write the admit orders and notes and make sure they're all tucked in before sign out. Staying to 9 wasn't uncommon in those situations, depending on the patient and your senior. Staying to midnight happened once or twice that I can recall.