The term of office of all commissioners, except any ex officio member, shall be for three years from the date of their election and until their successors are qualified and elected. However, of the first producer members of the commission, five shall serve for one year, five shall serve for two years, and five shall serve for three years, with the determination of term of each member to be made by lot at the time of election. Terms of office of each commissioner shall be limited to four consecutive terms, except that any member selected to serve a one-year term or a two-year term may serve one additional three-year term.