(1) It shall be the duty of the Commissioner to exercise the powers conferred on him or her by subsections (1) and (2) of section 19 from time to time in relation to each rating authority area so that the result referred to in subsection (2) is achieved.
(2) The result mentioned in subsection (1) is that a period of not less than 5 years and not more than 10 years elapses between the date on which any valuation list in relation to the area concerned is caused to be published under section 23 and the date on which the next subsequent valuation list in relation to that area is caused to be so published.