I really like the looks of the 6637 air filter mod for the 7.3l. I am going to order one today. How long can I expect one filter to last (miles) under normal conditions. I see most recommend you order two to save money but I only drive my truck about 5000 miles per year and if they last quite a few miles I did not want one sitting on the shelf for 5 years. Any advice would be appreciated. Thank you!