Any agreement authorized by § 47-1A-732 shall be:
(1) Set forth in the articles of incorporation or bylaws and approved by all persons who are shareholders at the time of the agreement, or in a written agreement that is signed by all persons who are shareholders at the time of the agreement and is made known to the corporation;
(2) Subject to amendment only by all persons who are shareholders at the time of the amendment, unless the agreement provides otherwise; and
(3) Valid for ten years, unless the agreement provides otherwise.