I normally don't book until I like the fare. Right now the August fares out of Wash. DC/Dulles are pretty high, so I'm waiting. Our normal fares tend to run around 79 each way, so I try to keep an eye on the rates and for sales. The prices tend to drop during the week days. I'm presently watching fares for January, May, and August, but haven't bought yet. We are pretty flexible too. Also, the size of your party is something you have to consider too. If you need many seats, sometimes you can't hang back and watch too long.