How often are you supposed to do the tests? It may reduce water changes but at what point does the cost of the tests outweigh any benefits in not doing WCs.
Water changes on large tanks can be a real pain and quite costly unless you have a fish room behind the tank with drains and auto changer etc. I'd much rather run an ICP test every 1-2 months than change large quantities of water which is time consuming and takes the help of my wife given the location of my water storage and drains (she doesn't appreciate that).