Except as otherwise provided in this chapter, within 30 days after declaration of the result of the election to organize a district, the 7 persons elected as commissioners shall meet and decide by lot the term for which each shall hold office. Three shall serve for 6 years; 2 shall serve for 4 years; and 2 shall serve for 2 years, respectively, from the date in the next even year an election would otherwise be held, as specified in § 719 of this title or until their successors shall be duly elected and qualified. It is the purpose of this section that the first members of the board shall serve until the date an election would otherwise be held in the next even year, in addition to their 6-, 4- and 2-year terms.