I wish I had ants... my problem is
raccoons marauding both my seed feeders and the hummingbird feeder. I've already lost one hummingbird feeder and had my passionflower vine mauled by the raccoons when I neglected to bring the feeders inside overnight.
Probably because I bring in the hummingbird feeder nightly (after losing the one feeder), I don't have much of a problem with ants. I keep the feeder in the kitchen sink overnight since it has a tendency to drip a bit. I replace the nectar at least once a week to keep it fresh and minimize bugs that way, as well.
I had two ruby-throated hummers that were ever-present fixtures around my feeder, but with the cooler weather of the past week I have not seen them at all, nor the black-chinned hummer that visited a couple times a week. They may have begun their southward migration for the winter. Nonetheless, feeders should be kept up until you're certain the hummers in your area have moved on. One rule of thumb suggests leaving them out at least two weeks AFTER you think you've seen your last hummingbird. Never know when the stragglers might show up for supper!
Here's some info about hummingbirds from the Texas Parks & Wildlife Department:
Texas Hummingbird Roundup (don't you just have images of cowboys out roping a bunch of wild hummingbirds...or is it just me?

)