If, at the end of a fiscal period the assessments collected are in excess of expenses incurred, each commodity committee, with the approval of the Secretary, may carry over such excess into subsequent fiscal periods as a reserve: Provided, That funds already in the reserve do not exceed approximately one fiscal period's expenses. Such reserve funds may be used (1) to cover any expenses authorized by this part and (2) to cover necessary expenses of liquidation in the event of termination of this part. If any such excess is not retained in a reserve, each handler entitled to a proportionate refund shall be credited with such refund against the operations of the following fiscal period or be paid such refund. Upon termination of this part, any funds not required to defray the necessary expenses of liquidation shall be disposed of in such manner as the Secretary may determine to be appropriate: Provided, That, to the extent practical, such funds shall be returned pro rata to the persons from whom such funds were collected.