Other arguments left over from pioneer days are that hydraulic systems will freeze. Not nearly as much as the main line and lateral piping! These must be blown out each fall. Blowout the hydraulic control system at the same time. The N/C types will blow water backward through the control tubing. You must sequence each station at the controller. Blowing the N/O systems will move pistons and diaphragms enough to evacuate most water from the pressure chambers and release pressure on the control tubing.