The association and its members may make and execute marketing contracts which require the members to sell, for any period of time not to exceed the productive life of the gas facilities or supplies, all or any specified part of any gas produced by the members exclusively to or through the association or any facilities of the association. If the members contract a sale to the association, title to the gas passes absolutely and unreservedly, except for recorded liens, to the association upon delivery or at any other specified time which is expressly and definitely agreed in the contract.