Of the board of directors elected at the next general election following creation of the district, three shall hold office for four years, and two shall hold office for two years, and until their successors are elected and qualified, the length of the respective terms to be determined by lot. Thereafter, at each general election, a number of directors corresponding to the number whose terms of office expire shall be elected for the term of four years. The terms of directors shall commence on the first Monday in January next following their election. [Amended by 1973 c.796 § 16; 1975 c.598 § 7; 1989 c.503 § 32; 2003 c.14 § 129]