I was going to take my feeder down, but I read that it's not necessary to take down feeders to force hummingbirds to leave. The initial urge to leave is triggered by the shortening length of sunlight as autumn approaches, and has nothing to do with temperature or the availability of food when the bird is fat enough, it migrates.
I also read that by this time, the birds you see at feeders are already migrating anyway. If you remove your feeder, birds will just feed elsewhere, but may not bother to return to your yard the next year. Hummingbird experts recommend continuing to maintain feeders until freezing becomes a problem, so I am going to keep my feeder up, just in case a straggler stops by for a drink.
Hopefully, he or she will remember my hospitality when they return in the Spring.