Over time, usually 5-10 years(varies depending on how much you feed/how much rock/sand you have), the rock/sand becomes saturated and then the tank starts having corals dying since you've been doing the same thing for so many years and the only reason why it has been kept in balance is because the rocks/sand has acted as your natural filters, but those filters are full now.
The most important part on changing water is vaccum all the fish waste thats just for me.. If you dont have any fish i think you can get away with it.