I can't think of any good reasons to do any advance bookings more than 21 days out except perhaps one is trying to get a seat on one of limited flights to China and you are trying to secure a spot. Otherwise, I assume the flight schedule from January onward will have significant changes, we now have no change fees, and at least on the routes I fly they don't appear to have any significant pricing incentives to book far ahead - and I also assume I could wake up any given day to local restrictions that will force me to cancel my plans anyway.