They tell you to plan on a day lasting until 5, I think, in case something goes wrong and they need to shuffle things around. But realistically, I can't imagine going much later than 3. They also asked if anyone had an early flight and needed accomodating.
Half of the interviewees interview in the morning and do the tour in the afternoon, which ends at 2. If you would save money or otherwise benefit from the early flight, I'm sure you could request to be in this group.