It is generally recommended to clean gutters at least twice a year in Oregon, once in the spring and once in the fall. This can vary depending on the specific climate and weather conditions in your area and the condition of your gutters. If you have a lot of trees near your home, you may need to clean your gutters more frequently as leaves and other debris can accumulate more quickly. You may also want to clean your gutters more frequently if you notice that they are clogged or if you see water spilling over the sides, which can be a sign that they are not functioning properly.