You can slowly reduce the dosage amounts until you find the optimum dosages for your tank. Just cut the amounts by about a quarter, then watch the plants for a few days to see if they continue to grow as well. If they do, cut the amounts by another quarter and repeat. Do this until you see the plants not doing as well, then go back to the last dosage amounts and continue with that. You can do this with one chemical at a time and get better results.
Once you have found the optimum dosages for your tank, and your conditions, you will have less excess nutrients in the water and you can increase the time between water changes, or the percentage of water you change each time. Just remember that if the tank changes - more plant mass, less plant mass, more light, more CO2, etc. - you may have to readjust the dosages.