The quality of your tap water also determines how long the filter will last, if there is hard water, sediment or rust particles for example in your water supply then those will decrease the life of your filter.
At least every two years you should have your Kangen machine deep cleaned and serviced by Enagic (the makers of Kangen water filters), you should have received a service request form when you purchased your Kangen or contact the distributor who sold you your Kangen to book you machine in for a service and filter clean.
Of course you need to maintain your machine well in order to extend itís life and think about how you use your Kangen, for example if you make strong acidic water for cleaning and then make slightly alkaline water for drinking, donít drink the first glass of water when switching from strong alkaline to weak alkaline as that first glass will have some remnants of the strong alkaline water in the pipes and filter and you donít want to be drinking strong alkaline water.
There is no need to change your Kangen water machine for a new model if your happy with the old model, a Kangen machine is capable of producing alkaline water for years and whilst new styles and new technologies do get introduced, the alkaline water wonít be changing so you can continue to drink water from an old (and serviced) Kangen machine.
Now if you have one of the old cartridge filter machines that where in manufacture before 2011 then your need to replace the cartridge every six months (as opposed to every twelve months for the new filters available from 2011 onwards), for reference a 6-month lifecycle is rated at 6,000 litres of water and a 12 month filter lifecycle is rated at 12,000 litres.
You can buy a citric acid cleaning powder from Enagic (the makers of the Kangen machine) and the SD-501 flagship Kangen water ioniser makes it easy to change filters.