During a recent semi-annual HVAC maintenance, the techs said we did not need the fiberglass filters at the wall since we have the electrostatic filters in the air handler in the attic. They stated that the fiberglass filters increase air drag on the unit motor(s) causing increased energy usage and shortening the life of the motor(s). Is this true? Of course, they also were trying to sell us on duct cleaning and a Knight Air ultraviolet cleaner (for $900). What is the truth? Is it time to find a new HVAC maintenance company?