How often you do water changes will depend on different aspects in your setup. Ocean water is extremely clean in comparison to water found inland. The lifeforms you want to keep, will determine how clean you need to keep your tank.Lifeforms that live near coastlines will need nutrients in the water column, that deepwater lifeforms cannot tolerate at all. How you need to keep your tank will be determined by what you wish to keep in it.
Since you wish to focus on dosing the additives and only make very few water changes, you will need to be on top of two things: organic detritus and nitrate buildup.
Therefore there will be two things you can do to lower your need of water changes, which is to have a huge sump and a huge skimmer. You can grow beneficial algae in the sump that assist in removing nitrates. An overpowered skimmer assist in removing organic compounds in the water column.
While you stock up your tank, you will need to do regular testing to keep an eye on the buildup of nitrates, and you need to keep an eye on your skimmer, which will help you judge how much pollution is in your water column: and that will determine how often you need to make water changes. If your nitrates run too high, fix it with a water change and if your skimmer cannot keep up with the organic detritus, fix it with a water change. Eventually you will know exactly what your tank needs and that is when you know for sure, how often it will need to have water changes.
I actually keep a nano in the exact opposite way, I never dose anything but make fairly regular water changes. I just don't like fiddling around with dosing anything and the only cnidarian I keep is one anemone so it gets everything covered that it needs from the water changes.
It all depends on what is right for your mood and what is right for your tank, and as I mentioned, remember to determine if you wish to keep lifeforms that can handle a degree of pollution or those that cannot and don't stop testing and keep developing your dosing parameters, until you are sure that nothing is changing in your tank. Remember that the salt mixes will have additional additives & adjust you don't overdose after water changes. Corals will have changing needs for nutrients as they grow and flourish and the less you do water changes, the more you need to do tests, to make sure that you know exactly how to dose your tank as it develops.
As people already pointed out, never add salt to the tank, nothing in a tank can tolerate the salt, so always make the water mix in accordance with the mixing instructions and allow the water to stir for long enough to get the salt crystals completely dissolved.
