As others have said nothing can go out of adjustment with wear to the threads. It is the lens flange that determines the focus distance, and as this can't wear, or only minimally over many decades, so it hardly matters if the threads are sloppy (which I've never come across), just so long as they can tighten up. But the brass threads on many Leica lenses are self lubricating anyway, so even if any chrome plating wears through it doesn't matter, even at the age LTM lenses are now they will still see you out.