A mutual savings bank may provide for pensions or retirement benefits for its disabled or superannuated employees or health insurance benefits for its employees and may pay a part or all of the cost of providing such pensions or benefits in accordance with a plan adopted by its board of trustees or a board committee, none of whose members is an officer of the bank. The board of trustees of a savings bank or such a committee of the board may set aside from current earnings reserves in such amounts as the board or the committee shall deem wise to provide for the payment of future pensions or benefits.