For those that run carbon passively in a filter bag or actively in a canister filter, once a week take the bag outside and smack it against the driveway a couple of times. Then rinse it to remove the fine particles and put back in your sump. You can quadruple the life of your carbon because each time you do this, you're exposing new surface area for adsorption. For those who run in reactors, you can still stretch out your carbon useage. Just run less and change more often. (Note: don't do this with the few Lignite-based carbons out there....it's highly friable and will just turn to dust. However, because of the price difference, most people tend to use bituminous coal carbons).