In the event a savings and loan association is converted to a mutual savings bank, any person, who at the time of such conversion was a director of the savings and loan association, may serve as a trustee of the mutual savings bank until he or she reaches the age of seventy-five years or until one year following the date of conversion of such savings and loan association, whichever is later. The bylaws of any mutual savings bank may modify this provision by requiring earlier retirement of any trustee affected hereby.