From my experience flying with Delta Air Lines, upgrades can clear anywhere from a few days before departure to right at the gate. I’ve had Medallion upgrades clear about 72 hours out on quieter routes, but on busy flights it didn’t happen until boarding started. It really depends on demand, your Medallion status, and how full the premium cabin is. I usually keep checking the app because seats can open suddenly. Honestly, the best way to instantly manage expectations—and quickly book, cancel, or modify flights—is to stay flexible and monitor your reservation closely as departure gets closer.