At any time during each year, the board shall prepare and publish a schedule of premiums or rates of insurance for subscribers, which schedule shall be printed and distributed free of charge to such persons who shall make application therefor, and any such subscriber may, at his option as hereinafter provided, pay to the fund the amount of premium appropriate, and upon payment thereof, shall be insured, as hereinafter provided, for the year for which such premium is paid, and such insurance shall cover all payments becoming due for which said premium is paid. The premium is fixed and shall be adequate to enable payment of all sums which may become due and payable under the provisions of this act, and adequate reserve sufficient to carry all policies and claims to maturity. In fixing the premiums payable by any subscriber, the board may take into account the condition of the premises of such subscriber in respect to the possibility of subsidence as shown by the report of any inspector appointed by the board or by the department, and they may from time to time change the amount of premiums payable by any of the subscribers as circumstances may require and the condition of the premises of such subscribers in respect to the possibility of subsidence may justify, and they may increase the premiums of any subscriber whose loss experience warrants such change. The insurance of any subscriber shall not be effective until he shall have paid in full the premium so fixed and determined.