It depends on the species and the age of the bird when the migration period actually stops. Latecomers (late-goers?) are typically juvenile birds, late season hatchlings that are still building up strength and body weight for that long trip south.

Continue to keep the feeder up and full at least 2 weeks after you last see any birds. Do not think that keeping the feeder going is preventing him from migrating. That is genetically programmed into the bird from countless generations of preceding birds - he will head south when his time is right :-)