Product review (4 stars): Works fine with a little help
These filters work as advertised with a little help. You can get about 4-6 weeks of use before the hard water minerals finally harden the filter to a rock. Of course it depends on how often and how high you run your humidifier. This winter has been unusually cold, so 4-5 weeks has been tops for me. The filter can begin to smell (like a wet dog) if not treated. I use just a couple drops of clorox in the tank when I fill for the first time and that will take care of it for at least a couple weeks. Re-treat if necessary.