Jo-Jo, In the past, you could stay in the park until 7 PM. At that time, they were checking wrist bands and moving non-party people to the front of the park / exit. Many people hang on Main St and do some retail therapy. We typically go in around 2 PM (AP), and go back to the front with our X-mass party tickets around 5.
Yes, people just going for the party can get in at 4, which gives them 8 hours (about the cost of a day pass), where as if you go at 8 AM you get 10 - 11 hours for about the same price. Yes we do get a special parade , fireworks and watered down Hot Chocolate and cookies (although I heard this year they are changing that), so it works out about the same. If you are concerned about the crowds, they cap the sale for the party tickets at 40,000.