In the end it's really simple. They monitor advance bookings. If they are strong then there will be no major discounts. The standard early booking fare from the ATL or CLT area is around 650.00. If the flight is booking up nicely then it's not likely to go below that price. If not then there will be discounting since a airline seat unlike most products is perishable. Once that aircraft pushes back the value of that seat is zero.
The balancing act is how to fill that seat before pushback with revenue but not cannibalize revenue from earlier bookings by training the consumer to wait. Airlines have become much better at in recent years. The key however has been capacity constraint. Some of that has been smarter fleet choices by management and more of it is maxing out our airport capacities. Runway slots and gates are hard to come by and planned infrastructure mprovements are virtually zero. Capacity changes now come from upguaging aircraft to larger sizes not additional airframes. In the STT market the opposite is happening. The airports length and terrain are forcing airlines into smaller airframes with fewer seats as Boeing 757's are retired. None of the replacement aircraft with the same capacity can get in and out of STT with a full load.
George