If you're in DC in the summer and feel like rolling the dice, request the gov per diem rate when booking your hotel (this has to be done directly with the hotel, no hotels.com tomfoolery). They may say you need to show gov id (which you're supposed to do) but this is my 3rd hotel so far and I haven't shown anything but my drivers license, while getting rates 150-250 below list. No one's asked me for anything. Still get full points/rewards tho.