Replacement purifier cartridges are designed to last 350 cycles (65 gal. / 250L) for GEOPRESS and 300 cycles (40 gal. / 150L) for UltraLight. Lifespan will decline when purifying water with high levels of silt, sediment or tannins. Cartridge press time increases towards the end of the cartridge lifespan; when press time reaches 25-30 seconds, the cartridge should be replaced. Cartridge continues to protect, even as press time increases.