If you take your hummingbird feeder down early in fall because you're afraid you'll keep the birds from migrating, relax. You're not keeping anyone.
Hummingbirds don't migrate because food runs out. They migrate because the days get shorter. A change in daylight triggers hormones that tell them it's time to go, and they go, full feeder or empty.
You can see it in the timing. Adult males leave weeks before females and young birds, while flowers are still blooming and feeders are still full. Nothing about your feeder can talk them out of it.
What your feeder does in fall is the opposite of trapping them. It fuels the late ones: young birds making their first trip south and migrants passing through from farther north. For them, a feeder is a gas station.
So leave it up until about two weeks after your last sighting. Keep the nectar fresh and clean, and let it help the latecomers.