Of course I appreciate these filter cartridges! But I can not know if a cartridge that "has had its day" and not replaced on time, dropped all its "pollution" retained in the water that continues to filter with or if it no longer filters all simply. In short, it is imperative to throw a cartridge reached saturation on pain of severe intoxication? Furthermore the cursor position on the display is independent I believe the number of liters filtered, it decreases with time, and record indicates that with a cartridge can be filtered so many liters of water. I need to check if a cartridge corresponds to 1 month since 12 cartridges / 12 months for the use that I made.