Elevator Etiquette

If you are getting into an elevator to go to the top floor, should you be courteous and let other people in ahead of you? Won't they be trapped by you when they try to get out, which is more annoying than being the last one in? This is the dilemma I face every day at work, where I exit the elevator on the 12th and top floor. Interestingly, I am on the receiving side of this gesture in my apartment building, as I live on the 3rd floor. I have been boxed in not only by the polite elevator riders, but also by my own large bags of purchases, trying to fight my way out of the elevator mere seconds after entering. I guess I'll take the courtesy, as long as they press the button for me.