ORS § 107.475
The court shall determine and fix in its judgment the duration of the separation. At the expiration of such time, the judgment shall have no further effect. However, no rights created or granted in the judgment which have vested shall be affected by its termination. Upon motion of a party and service upon the other party of notice in the manner provided by law for service of summons, the court may renew or extend the duration. When the judgment is for unlimited separation, a party may by motion alleging that the cause for separation no longer exists and after due service of notice upon the other party in the manner provided by law for service of summons, apply for an order modifying or vacating the judgment, subject to the provisions of ORS 107.135.
ORS 107.475