I think I've read that hummers have a regular "route" that they take, and pass on to future generations. If you're on a migration route, you will always have tons of hummers at migration time.
Places with permanent resident populations have it a little more complicated in that you need to attract some hummers off their regular route to visit your yard. Certainly planting the plants they like will help with this, and then if you install feeders as well, you may get more since there is a good regular food source. Then you will be on their route and probably see them more and more as they pass the info on to their progeny.
