The general management of the business of a county mutual insurance company must be vested in a board of directors consisting of no fewer than five members nor more than fifteen members. The members of the board must be elected by the members of the company at the annual meeting in the manner provided by the bylaws of the company. As nearly as may be, one-third of the members of the first board must be elected for one year, one-third for two years, and one-third for three years, and in all future elections, except in the case of elections to fill vacancies on the board, members must be elected for terms of three years. Each director holds office until a successor is elected and qualified. In the election of the members of the first board, each incorporator is entitled to one vote, and at every subsequent election each member of the company is entitled to one vote per policy. The board may exercise the usual powers and shall perform the usual duties of a board of directors of a corporation generally.