The liability of a surety on any bond required by this part shall be terminated only as to operations on and after the effective date of a superseding bond, or the date of approval of the discontinuance of operations by the export warehouse proprietor, or otherwise in accordance with the termination provisions of the bond. The surety shall remain bound in respect of any liability for unpaid taxes, penalties, and interest, not in excess of the amount of the bond, incurred by the proprietor while the bond is in force.