Oregon Revised Statutes Public Financial Administration § 294.135

(a) The custodial officer may make investments having a maturity longer than 18 months when the governing body of the county, municipality, school district or other political subdivision to which the funds belong has adopted a written investment policy that, prior to adoption, was submitted to the Oregon Short Term Fund Board for review and comment to the governing body, that includes guidelines concerning maximum investment maturity dates and that provides by its terms for readoption not less than annually; or

(b) When the funds in question are being accumulated for an anticipated use that will occur more than 18 months after the funds are invested, then, upon the approval of the governing body of the county, municipality, school district or other political subdivision, the maturity of the investment or investments made with the funds may occur when the funds are expected to be used.