Imho....standing water is not a good thing in a chameleon cage and if I were going to run a misting system I would be making sure that it was done in such a way that any standing water in the cage could be gotten rid of on an almost daily basis. Imho... I would not even be contemplating how long I could leave the water before it might become dangerous, I would be making sure it never came to the point of even having to think about it. I would be putting the chameleon's best interests ahead of anything else.