With ChillCel Pads, you should expect to change these every 7 or 8 years. This can vary with water quality and local conditions.

WARNING With any filter pad, failure to replace filter pads or evaporative cooling pads when they are past their useful life may result in reduced efficiency/performance of the air conditioner. Water may carry over into the ductwork and/or electrics, which may result in expensive damage and repairs.