From and after January 1, 1928, it shall be unlawful for any association to issue or deliver in this state a policy unless the same shall contain in substance provision that except as otherwise expressly provided by law the policy shall be incontestable after it has been in force during the lifetime of the insured for a period not more than two years from its date, except for nonpayment of premiums and except for violations of the conditions of the policy relating to military and naval service in time of war, and at the option of the company, provisions relative to benefits in the event of total and permanent disability and provisions which grant additional insurance specifically against death by accident may also be excepted; but upon the maturity of any policy or certificate, the secretary of the association shall proceed to make the necessary assessment with which to raise funds to pay the same and upon receipt of such fund shall within thirty days pay the same over to the beneficiary under such maturing certificate or policy.