Any pension payment or retirement or health insurance benefits payable by a mutual savings bank to a former officer or employee, or to a person or persons entitled thereto by virtue of service performed by such officer or employee, in the discretion of a majority of all the trustees of such bank, may be supplemented from time to time. The board of trustees of a savings bank or a board committee, none of whose members is an officer of the bank, may set aside from current earnings, reserves in such amounts as the board or the committee shall deem appropriate to provide for the payments of future supplemental payments.