A group health insurance policy shall contain a provision that all benefits payable under the policy other than benefits for loss of time will be payable not more than 60 days after receipt of proof, and that, subject to due proof of loss, all accrued benefits payable under the policy for loss of time will be paid not less frequently than monthly during the continuance of the period for which the insurer is liable, and that any balance remaining unpaid at the termination of such period will be paid as soon as possible after receipt of such proof.