3) Wind-turbine mechanic
Once a wind turbine is built in the factory and erected in a wind farm, someone needs to keep it tuned. Turbines are basically giant motors that come complete with all the complexities of a typical modern car. You bring your car to an auto mechanic; wind mechanics have to bring themselves to the turbine. Keeping the turbines tuned and in good operating condition makes good business sense for the wind farm owners (inefficiency bleeds dollars), so it's not hard to see how being a wind-turbine mechanic is a great way to keep working until retirement.