When they wear out I rinse mine in used tank water over and over until they wear out.
I only have two tanks I use anykind of filter cartridge with, the rest I use sponges in the filters and you don't throw them away for years.
Butterfly, That is what I was figuring I should do, because my filter cartridge is still working good, but is 2 1/2 months old.. I was just gonna rinse it in the old tank water when I did my water change tonight and put it right back it
I never change my filters, but I don't use filter cartriges - just filter floss and sponges (and Purigen in a couple of tanks). They get a rinse-out in old tank water during my weekly water changes and that's it.