An agricultural association may contract with any member for the member’s exclusive sale to or through it, of all or any part of the member’s agricultural products or other designated commodities. Such contracts may permit the association to take and sell the property without acquiring title thereto, and pay the member the sale price less costs and expenses of selling, which may include the member’s pro rata portion of the association’s annual outlay for overhead, interest, preferred dividends, reserves or other specified charges. Such contracts must be for a specified time, not less than one year. Each contract shall fix a period of at least ten days during each year after the first, within which either party may terminate it without affecting any liability previously accrued.