You may want to check with your resort. If you stay past 4pm you might not only be responsible for your cab fare back to your "home" resort, they may ask you to purchase a half day pass if you want to stay into the evening for dinner. I'm not positive this is the case, but you would definitely want to know your options before you stay beyond 4pm.
I don't think you can stay past 4p. I know people were saying that if you wanted to go back early you had to take a cab, but I haven't seen anything on someone staying late. Hopefully you'll get a for sure answer from someone.