We have been using these water filters for almost ten years now.
We started just changing them every six months. We are now changing out these filters in 90-100 cycles not because they aren’t doing the job but just the opposite. I noticed the filters getting dirtier in our six month change cycle. I then moved it to every 120 plus days now I am at about 90-100 days. We might be at a strict 90 day change cycle because of the crap in our city water.

I trust these filters. When I first bought them I sent filtered samples of water off to be tested. We got back stellar results. Our water tastes great too. I highly recommend these filters.

MERCHANT COMMENT:
Thanks for much for taking the time to share your experience. Please note, your system has various stages of filtration and many layers on each stage, so just because you see the exterior of your cartridge turn dark colored, chances are this is just the outer layer and the inner layer is still clean (if you look with a flashlight through the top hole on the SuperBlock Cartridge) and then you still have other stages after this too. As such, you don't need to waste money buying more cartridges so often, simply follow our cartridge change recommendation of every 500 gallons or 12 months, whichever comes FIRST).