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I've used a pressure tank in a domestic setting for 15 years. The proportion of the tank that is taken up by water depends on the pump pressure and the air pressure and the start and stop pressures. The amount of water supplied between pump stop and restart depends on the range set by the pressure sensitive switch and the charging pressure of the air bladders.

These switches usually have an adjustable point, but you will need pressure gauges to estimate the stop and start points. All of this means that the amount of water supplied by the system with the pump off is not a simple proportion of the tank volume. Also, you need to have some water in the tank when the pump switches on, otherwise you risk the pressure never dropping enough to trigger pump start.

Having several tanks makes the behaviour more complex. You can use a tank with a lower air charging pressure than the others to provide a switch on point even after the other tanks are empty of water. This approach can give you the best use of the available volume. However, getting the most use out of the available volume implies a big difference between start and stop pressure.

Usual maintenance problems are loss of air from the tank (giving really short cycle times) and failure of the cheap pressure switch.