I asked the same question on the chem forum a while back, and the advice I got was to wait and see if I need it, then do it if I have a reason to. If your system is stable and you are happy with everything, I would say let things be. Dosing carbon is not some magic formula, its done for a reason. Now, if you wanted to add more fish, increase bioload, increase feeding, or had SPS corals that may be a little brown from moderate nutrients in the water, then that would be a reason to start. I started because I was struggling with high nitrates, and I went from 2 fish to 8 rather quickly in a small tank. Hope that helps.