The Explorer was rated at "up to 500 gallons"
I have had the Hiker for about 10 years, still use it occasionally with the original cartridge.
Before I use it I put a few drops of bleach in a mug of water and pump that through. Then I run a few liters of tap water through it .
(I don't count this as "usage")
BTW, that is unscented bleach.....
Franco