We have OREO appraisals addressed in our policy. We're a Fed bank and the exam manual says:
A bank should have a policy for periodically determining the fair value of its OREO property by obtaining an appraisal or an evaluation, as appropriate. While the Federal Reserve has no prescribed time frame for when a bank should reappraise or reevaluate its OREO property, the bank’s policy should conform to state law, if applicable, and take into account the volatility of the local real estate market. A bank should determine whether there have been material changes to the underlying assumptions in the appraisal or valuation that have affected the original estimate of value. If material changes have occurred, the bank should obtain a new appraisal or evaluation based on assumptions that reflect the changed conditions.
Hope that helps. And do check your state law.