In the case of any plan of life insurance which provides for future premium determination, the amounts of which are to be determined by the insurance company based on then estimates of future experience, or in the case of any plan of life insurance or annuity which is of such a nature that the minimum reserves cannot be determined by the methods described in RCW 48.74.040 and 48.74.070, the reserves which are held under any such plan must, under regulations promulgated by the commissioner:

(1) Be appropriate in relation to the benefits and the pattern of premiums for that plan; and

(2) Be computed by a method which is consistent with the principles of this standard valuation law.