When the insurance reserve fund provided for in Section 10-7-130 reaches the sum of five per cent of the total insurance in force, then annually thereafter the State Budget and Control Board shall proportionately decrease the premium of insurance to an amount which will be sufficient to maintain the insurance fund at five per cent of the total insurance in force, and if in the judgment of the board the income from the investment of the insurance sinking fund is sufficient to maintain the insurance fund at five per cent of the total insurance in force, no premium shall be charged for the ensuing year, except that no building or property insured by the board shall cease to pay premiums until five annual payments shall have been paid even though such payments increase such insurance sinking fund beyond the sum equal to five per cent of the total insurance in force.