The website states the following: 1 MAXTRA+ filter cartridge lasts up to 4 weeks or 100l of filtered water.

Very much so, from my point of view. There is an indicator on the jug that shows whether the cartridge should be replaced. With this, probably 100 - 150 litres go through. Then I set the counter to 0 again and leave the cartridge in. With our water, the limescale is still filtered out well. The filter has to be changed at the latest when slight limescale marks form in the filtered area on the wall of the jug. So according to my calculation, after about 300 litres.