You only need to maintain a particular level of ammonia until the tank has completed the 1st stage of the cycling process. Your first stage of the cycling process is complete when you have enough ammonia==>nitrite bacteria in your tank to handle the daily amount of ammonia you expect the fish will eventually produce.
If you continue to try to force a particular ppm level of ammonia in the tank, you are just going to grow more ammonia==>nitrite bacteria than you need, and in the process send nitrite through the roof because there will not be enough nitrite==>nitrate bacteria in the tank to handle all the nitrite being produced from the ever increasing amount of ammonia you would have to add to the tank to maintain some particular level.
While I don't have enough practical experience to say exactly when you can consider a tank to have completed this 1st stage of the cycle, I would estimate that you can consider the 1st stage complete when you can add about two drops of ammonia per 10 gallons of water per day and 24 hours later you get an ammonia reading of 0ppm. Once you reach that level, you only need to keep adding that 2 drops / 10 gallons daily to maintain the ammonia==>nitrite bacteria levels while the nitrite==>nitrate bacteria try to catch up. Even then, it's very easy for nitrite levels to go through the roof because it's relatively easy to grow the ammonia==>nitrite bacteria, but the nitrite==>nitrate bacteria are a little bit harder to get going. Until that 2nd set of bacteria really gets going, all that ammonia you are adding to the tank gets converted to nitrite with nothing in the tank to convert the nitrite to nitrate.
So yes, once your tank can convert 2 drops of ammonia per 10 gallons of tank water per day into nitrite, quit testing ammonia levels and just keep adding that level of ammonia feeding.
Again, my number of 2 drops per 10 gallons is just an estimate. An exact number would be more dependant on the stock level you plan to have in the tank once it's fully cycled.
