Every 12,000 miles or every four oil changes is the recommended filter change/cleaning interval. However, my engine guru contacts recommend that you do it based on the air quality. They say 12000 miles is too long in the dusty summer or fall weather. If crops are being harvested around your common driving area, this is a big dust producer. Probably second only to gravel or dirt road driving. I never take 03 Si down gravel more than five times a year. When I do drive at <5mph. I live in a rural farming area. So my personal approach is to clean my short ram filter every 6-8k during the summer and fall. Then after all the crops are in(usually late Oct. early Nov.), I clean my filter and don't clean it again until Feb. or March. Winter air in Indiana has very little particulate content(pollen, dust, etc...) ALSO EVERY TIME YOU CLEAN YOUR FILTER YOU SHOULD CAREFULLY, AND I MEAN CAREFULLY CLEAN YOUR MASS AIR FLOW SENSOR(which should be inserted somewhere on your short ram). Neglecting to clean your MAFS every time you clean your filter can drastically reduce performance and cause your check engine light to come on. Obviously I am very anal about my civic, but it runs just as strong today as it did when I bought it almost 100k miles ago(and I'm still on factory plugs and wires).