All of my hubs have been balanced. There is a 1/4 inch piece of plate welded to each one at some point on the outside. It is the same color as the rest of the hub so it is hard to spot but it is there.
Balancing may not gain you mileage but it definitely prevents wear and tear on your suspension and trailer contents, as do shock absorbers. Both of these things are so cheap compared to the benefits that you are just being stubborn if you are not adding them to your trailer. $100,000 for a new truck and trailer, spend the $200 it takes to balance and add shocks.
