SPG, Marriott, and Hilton offer a 5th night free when paying with points. This is a great bargain, if you plan on staying 5 nights. It is also beneficial if you are staying 4 nights. Book a 5th night for the end of your stay and you have a guaranteed late check out. Add the Make a Green Choice card (at SPG) for some bonus points. The 5th night also counts for elite status. You are also protected in case of flight issues that could keep you in town an extra night.