I think that from now on I'm going to stock my aquariums with the following assessment: if your nitrAte readings prior to your weekly water change are at 20ppm or lower, and your fish have plenty of swimming room, then you're not overstocked.
People's situations are always very different. Some will have very few fish, plastic plants, and only do 20% water changes, and be able to keep nitrAtes under control. Others will have a large number of fish, heavily planted tank, and do 50% PWC weekly, and also keep nitrAtes at 20ppm or less. It really depends on the aquarium and your desire to keep it healthy.
That said, I wouldn't stock a tank to the max right away. Stock the tank slowly over time and see where your nitrAte readings are prior to your weekly PWC. If nitrAtes are well in hand with minimum maintenance, feel free to add some more fish. If not, increase how much water is changed and add some plants. Eventually you'll reach a happy medium where you have both the fish and maintenance schedule you want.