They simply save on service brakes. But they do require heavier valve springs. Most of the kits include them. Cummins recommends ONLY paper elements. If we stop all the dirt, we'll also stop air.
Air filters cause air restrictions.
Once the air restriction increases, the air filter needs to be changed. There is more harm done by pulling the air filter out, looking at it, blowing on it, etc. , than in leaving it in place and taking the reading from the outside gauge. That's why the outside gauge is there. The symptoms of air restriction are smoke and poor fuel mileage. A new filter will have an air restriction which equals approximately 12 inches of water.