I only have 6 months. I would like to give 4 or 5 stars but it doesn't work properly. I ordered around Christmas to have it for New Year's (and it would be easier to remember to change it quarterly). He did a very good job. first, but when after 3 months the red light came on and I put in a new cartridge on 4/1/17, the light didn't turn green again. I just (07/02/17) put in the 2nd new filter cartridge (3 months to go), let it rinse again for 5 minutes and it still flashes red when I turn it on :-/ Since the water is flowing through the unit, clean, me hope it's just a light that broke - and hope to get a replacement from the seller/manufacturer (I think it's a 2 year warranty). I will update later. Update: I called customer service and the woman was very helpful. She said that in the section where you put the filter, there is a little lever that sometimes gets stuck. You just have to click on it to reset it to make it appear again. Still working well and it's now early 2019.