These pre-filters need to be changed much less often, if at all, than the main filter. My pre-filter is perfectly rinsed with water. I can see how the pre-filter might need to be replaced if you're sucking in something that gets stuck in the pre-filter holes like blackberry seeds or something like that. But my pre-filters will sit idle for a long time, taking up space before I use them. However, this product does exactly what it was designed to do.