You can dose per the EI dosages forever if you wish, and if you continue doing 50% water changes every week or so. Or, you can "adjust accordingly", which means reducing the dosages a bit, watching the plants for a week to be sure they continue to grow as well, and repeating this until you see the plants don't do as well, then go back to the last dosage where the plants did well. You need to do this with only one chemical at a time, starting with KNO3, for example. Then KH2PO4, then CSM+B, etc. Once you have "adjusted accordingly" you can relax on the water changes, doing them less frequently or in a smaller percentage at a time. Just be aware that the dosages needed are proportional to the mass of the plants in the tank - the more plants, the higher the needed dosages, all else being equal. That seems like work to me, so I just use the EI dosages, adjusted downward a bit because I use low light.