You can also get mold, fungus, and heavy bacterial growth if the viv is too damp. I know - I have had it in my cages on some occasions, such as when water bowls got dumped!
I have never misted a corn (I have misted a few tree boas and tree vipers though). And I have never actually measured the humidity in the cage (well, maybe I did back in the '80s when I first started breeding corns). Basically, I found that if the snake is shedding in one piece, eating and digesting properly, and the cage isn't TOO damp, causing mold and fungus, then the humidity is probably ok. Better to keep it a little on the dry side (as long as the sheds are good), rather than too wet.
If the snake is having difficulty shedding, it is probably too dry, and a moist shed box is needed, and is usually the simplest fix. It is probably a nice idea to have some idea what your humidity is, especially if you are just starting out. But the snake will tell you if it is too dry if you just watch him shed.