OMG with four dogs we go through the filter every 4-6 weeks depending on the time of year and molting factor. They are cheap enough to change them that often. They work very well, better than the one that came with Neato. Very happy with them. I'll be looking for a big box of filters in a few months as we're going through them so quickly. I think the average filter price was around $2/month for a filter that can't be argued with. I love our Neato. We have a Golden Retriever (she sheds a bit in spring), a Labrador (she sheds something terrible), a Labradoodle (who sheds like a Yeti), and a non-shedding Goldendoodle (but every blade of grass sticks to it with Velcro). I start our car every day.