Every medical service corporation shall maintain at all times proper reserves, subject to the approval of the Commissioner, for unearned subscription fees and unearned premiums and for unpaid medical service bills, including provision for unreported and undischarged medical cases and other known liabilities. In addition, a contingency or epidemic reserve shall be accumulated annually at the rate of not less than 2 1/2 percent of net premium income. When such contingency or epidemic reserve equals $75,000.00 or 55 percent of the annual premium income (whichever is higher), further accumulations may be discontinued for any length of time that they are not required to meet the above requirements.