A life insurer shall determine the adjustable interest rate under Section 1110.004(b)(2) at regular intervals at least once every 12 months but not more frequently than once in any three-month period. At the intervals specified in the life insurance policy, the insurer:
(1) may increase the rate charged when the interest rate determined under Section 1110.004(b)(2) would result in a rate increase of at least one-half of one percent per year; and
(2) shall reduce the rate charged when the interest rate determined under Section 1110.004(b)(2) would result in a rate decrease of at least one-half of one percent per year.