I've known and read that running a 2 to 3 inch sand bed is the most practical way to do it. But I have seen and read that running a sand bed that is deeper can be beneficial but if disturbed can cause major issues. I've wanted to try it myself and see what the out come would be. I also knew a guy that never did a water change and his tank looked amazing. There was growth everywhere. What needs to be done to minimize water changes.
I think the whole deep deep sand bed thing is an old way of thinking. 2 or 3 inches is fine. I like having sand as it looks good and gives tiny creatures a place to hide. That being said, you don't need it. Many successful reefs are run with no sand at all.
To minimize or eliminate water changes you just need adequate filtration for the bioload your critters are putting out. And if it's a reef tank you will also want to supplement your tank with things like 2 part calcium and alkalinity mix and trace element additives.
I've run a DSB before (w/ plenum...i.e. OOOLD School) and had success with it. I did use only live rock in the tank and it wasn't long before it was loaded with life. I think that is a key, lots of and a variety of micro fauna in there. Along with some of the larger critters (I had some Nassarius snails in there).
It also helped hide my eel tubes that I had built so that was handy.
I'm not sure it is the answer to no water changes or the end all be all by itself. It's going to be like a lot of other things if not properly managed or maintained it's going to cause issues.