I voted "3 days a month in sump", but in actuality what I do is run carbon whenever I feel there is something in my tank that shouldn't be there. I leave the carbon in my overflow cup (since it is really the smallest bottleneck of flow) and remove it after about 3 days.
92-gallon corner tank, 100lbs of LR
, 140lbs of sand, 250watt 10,000K MH
, 110watts of actinic PCs, Mag 7 return, custom refugium, AquaC EV180 w/ Mag 5
Female lyretail anthias, eyelash blenny, tomato clown, saddleback clown, firefish goby, 2 sand-sifting stars