The Vario filter is based of its Filter Cartridge with Activated Carbon Core. This means that all the gunk in the water is trapped between the carbon particles inside the filter. After a while the carbon will get very full of gunk and it will stop working as well. Luckily there is no need to replace the whole filter, you just need to change the carbon inside with this carbon refill.
Activated Carbon capacity depends on water quality. Normal effective lifespan of carbon is 50 gallons (200 liters). High chemical or odor concentration can reduce the capacity of the carbon. Replace the carbon when you notice a change in taste or odor after filtering or after 6 months of constant use - whichever comes first.