Most expire October 31. Some expire in two or three-month segments throughout the one year period.
Most of the lodging and transportation coupons are valid through December 31. Haven't used the lodging section, but since the card expires October 31, best guess is you would need to make the reservation prior to that date. In 2004, the car rental coupons were valid through December 31. That's the only coupon I used in the entire book (paid $10 late in the season) and saved over $50 on the rental car in December!