As JamesQ said, the award ticket is valid for 1 year from the date of ticketing (on AA.) So if you booked an award ticket on July 15th, 2012 for travel on January 15, 2013, you could extend the flight by as much as 6 months. That's the one downfall of booking award flights 300+ days in advance...if something comes up and you need to delay, you don't have much time remaining to do so as your year is nearly up.