(a) Upon any liquidation of a domestic mutual insurer, its assets remaining after discharge of its indebtedness, policy obligations, repayment of contributed or borrowed surplus, if any, and expenses of administration shall be distributed to existing persons who were its members at any time within 36 months next preceding the date such liquidation was authorized or ordered or date of last termination of the insurer's certificate of authority, whichever date is the earlier; except, that if the commissioner has reason to believe that those in charge of the management of the insurer have caused or encouraged the reduction of the number of members of the insurer in anticipation of liquidation and for the purpose of reducing thereby the number of persons who may be entitled to share in distribution of the insurer's assets, he may enlarge the 36-month qualification period provided for in this subsection by such additional period as he may deem to be reasonable.

(b) The distributive share of each such member shall be in the proportion that the aggregate premiums earned by the insurer on the policies of the member during the combined periods of his membership bear to the aggregate of all premiums so earned on the policies of all such members. The insurer may, and if a life insurer shall, make a reasonable classification of its policies so held by such members and a formula based upon such classification for determining the equitable distributive share of each such member. Such classification and formula shall be subject to the approval of the commissioner.