Sending the app in Dec 1st is a way to help yourself and is more of a plus than a requirement that counts against you if not fulfilled. Even if it does have a small negative effect on your chances, having your essays not be at their best is a much, much bigger deal. Try to get your essays ready by Dec 1, but if you can't, take the extra time, try to get your app in as soon as possible, and make your essays the best they can be.*
*But not better than mine.
I don't want to get rejected. JK, JK.