The ceramic filter should be replaced at the latest when the diameter of the ceramic is too small to provide effective filter performance. The supplied measuring gauge helps to determine the right time to replace the ceramic filter. If your ceramic has a hairline crack, there is a risk of a bypass and the element should be exchanged too.
Glass fibre:The glass fibre filter must be replaced when it becomes physically difficult to pump water through it. This point in time is hardly measurable. If back pressure occurs, caution is required.
Hollow fibre:
The hollow fibre filter, as used in the BeFree products, should definitely be replaced if the integrity test described in the manual fails or if the flow is severely restricted. Further tips can be found here.
Activated carbon:
Activated carbon must be replaced according to instructions (usually this is 1/2 year after first use). In the Hiker water filter as well as in the filter cartridges for Drip, Expedition, Household filter & Co. this is permanently integrated and the complete filter must be replaced. Other filters, such as the Combi, are supplied with an activated carbon cartridge, which is removable and can be refilled.