I booked our Dec.-Jan. trip already; I figure that I want the airline to see sold tickets on that flight, and if it gets canceled, I'll just get a refund or voucher that I'll use anyway. I found that the fares were extremely sensitive to the day of the week in unusual ways; look at the date grid for airfares and see if it's the same for you. Interestingly, Christmas day was an expensive day to fly; it's usually cheap.