There's no mystery here. The 128K RT awards have a 60-day advance purchase requirement and are good for travel through Sep 4th. That currently puts you at Aug 19th for departures to meet the requirements. All you have to do to discover this is click on the Fare Rules link. It's not that hard. These rewards have actually been around for several months now (and have been noted on the DL forum), but you need to pay attention to the AP requirements.