I could write a similar review, but I checked online before calling the company. The website has a page that explains that in areas with high total dissolved solids [TDS] the filters will have a shorter working life. They acknowledge that with such high TDS counts, the filters will only last for about eight gallons. They suggest contacting the company in order to consider together more economical solutions to filtering the water.
In any filter, once it has been 'exhausted' it will begin to deposit the TDS that it previously removed back into the water as it passes through the filter. Any filter should be replaced when it is exhausted. In my case, until I had the monitor included in my Zero Water pitcher purchase, I didn't know when the water filters were exhausted.
You can appreciate that everything that tastes and smells so yucky was in your water and was removed by the filter. I wish I had water with fewer TDS so I could use the Zero Water pitcher. I'm giving mine to someone who uses city water and can use it economically. I'll probably give Zero Water a call and see what they suggest for filtering or purifying my well water . . .
In summary, the company is honest on its website. Perhaps they could make the limits of the product more prominent in the packaging, so people wouldn't be disappointed after finding out they will need to replace the filters so frequently.