The board of county commissioners may at any time reexamine the properties on any roll, and upon receipt of a petition from the board of supervisors of the district or the written request of a property owner shall do so. If it is found that the condition of such property or properties has changed so that such property should be eliminated from any rolls on file, or the valuation against which dollar rate is levied should be lowered, it shall so determine and enter an order adjusting the valuation as to such properties and shall certify and file a copy thereof with the treasurer of the county wherein the property is situated, and the treasurer shall alter and change the existing rolls accordingly. Valuations may be revised periodically to reflect changes in real property valuations by the county assessor.