This joint agreement creating and establishing the Lake Musconetcong Regional Planning Board shall have an indefinite duration. It may be terminated by a vote of two-thirds (2/3) of the full authorized membership thereof or by the adoption of an ordinance by one of the constituent municipalities terminating its participation. Upon termination of the Regional Board pursuant to one of these two methods, the effective date of termination shall be as agreed to unanimously by the full authorized membership-of the Board. In the event unanimous agreement cannot be reached, termination shall be effective on the June 30th next succeeding the expiration of twelve (12) full calendar months following the decision to terminate.