Performance car air filters should last indefinitely, if they are cared for properly. These filters are re-useable, and need to be cleaned periodically. The cleaning is accomplished using a cleaner specified, and produced by the filter manufacturer. However, common household detergents can be substituted if the recommended cleaner is a simple soap. Additionally, once the cleaning has been completed, a specialized treatment is then applied to the filter element. This treatment, which is usually some form of oil, promotes better dirt collection, and protects the filter element from degrading under the demanding conditions of the high performance engine.
For more info, see How to Clean an Air Filter