Well, sometimes, as they get older, the auto hubs are no longer auto and most of the time they stay engaged increasing wear and using up fuel with the extra drag. Also, my 97 4x4 had its auto hubs changed by the previous owner to WARN manual locking hubs. He stated that the original hubs had splines that were only a 1/4 inch wide while the WARN splines were 1/2 inch so I would imagine they would be stronger and lest probe to wearing out early. Now I live in Northern CA. So its not a big deal for me to get out and change them manually. Most 4x4er's I know prefer manual hubs. This way they KNOW for sure they are either engaged or not.