Once commercial recovery is achieved, the Administrator shall, within reasonable limits and taking into consideration all relevant factors, require the permittee to maintain commercial recovery throughout the period of the permit; except that the Administrator shall for good cause shown, including force majeure, adverse economic conditions, or other circumstances beyond the control of the permittee, authorize the temporary suspension of commercial recovery activities. The duration of such a suspension shall not exceed one year at any one time, unless the Administrator determines that conditions justify an extension of the suspension.