Your clock's movement is a mechanical device which requires a service schedule to keep it running. You may relate the workings to your car's engine. As with your car's engine, your clock's parts are metal on metal. The main determining factor in how many years the parts last is keeping the clock well lubricated by having it oiled periodically.
As time goes by oil starts to break down and dry out. By running a clock movement that isn't sufficiently lubricated you are cutting short the life of the movement.
We recommend an oiling every three years for all mechanical clocks. With the proper service a well made clock movement should last many lifetimes passing down from generation to generation.
Howard Miller Owner's Manuals