If you buy the 2003 book, the hotel discounts are good for that whole year, as long as the hotels still have rooms available for that special Entertainment Book rate. The hotels usually only reserve a certain number of rooms for the ERate.
Last month, I called to book Royal Pacific for July 2003 and said I want the Entertainment rate. They gave it to me and then when the 2003 Entertainment Book came out a couple of weeks ago, I bought one through my son's elementary school. So now I have the card to show when I check in, and I have all these discounts to use around my own city.