I started looking at Thanksgiving week fares in May last year and booked in August. Same high fare classes and prices both months. Periodic checks until departure did not show any drops, and yes the plane was totally empty in May and had less than a dozen seats sold in August. As GagaPilot said, DL knows they will sell out the planes at these prices or higher since that is when people feel they have travel. Do not expect lower fares for the holidays as time goes by.