According to the University of Kentucky, hummingbirds migrate even if feeders are still available. The hummingbirds know when to leave and full feeders don't disrupt their natural migratory pattern.
Migrating hummingbirds could obtain extra energy for their flight from feeders. According to the University of Kentucky, you can stop filling hummingbird feeders when the birds stop coming.
Sometimes hummingbirds visit feeders even in the middle of winter. The University of Kentucky reports that some hummingbirds were spotted from November to January in various parts of the state. Keep filling the feeders through winter to spot these hummingbirds.