This will depend entirely on driving conditions and the amount of miles driven. Generally speaking we recommend changing the Pre-Filter every 6-12 months.   Your Pre-Filter may actually deflect debris for a longer period of time, however, the water repellency feature will be less effective over time and cleanings. Washing your Pre-Filter prematurely or washing your Pre-Filter with a non Outerwears branded cleaner will reduce your Pre-Filers ability to repel water. If your vehicle or driving conditions expose your filter to extreme moisture or splashes of water, we highly recommend changing your Pre-filter every 6-12 months.
Pre-Filters are recommend to be changed every 6-12 months