All thats really been done is the adopting of a new habit. If you lucid dream less, you slip back into old habits. I don't know the specifics, but its probably not doing any damage. I mean if your lucid dreaming literally every night from when you start dreaming to when you wake, then maybe you need to cut back. But with it not being the case with most people, it cannot do much damage. If you lucid dream literally from when you start dreaming to when you wake, i think it can cause you to not get as well a nights sleep, but thats if you do it like on a daily basis.

Then again, i could be wrong.