I just got this for my husband to use at work in his office. It goes on and off every 30 seconds, and in this mode it will diffuse for 8 hours. He started it when he started work, and it went off right as he was getting done. Not bad for a little diffuser.
I am assuming it does. I have not witnessed it turn off. I find it turned off completely. The color changing is very soothing and pretty with a varied array of colors. I gave one to my mother and sister and they are very pleased as well. The unit does have two switches . One controls the light and one controls the mist. You can operate them independent of one another. The mister will not turn on if it is void of water.
The mist will only be too strong if you add an excess amount of oil. I typically only put 2 or 3 drops in the tank when it's full. A small area around where you have it sitting does get slightly moist.
The directions don't state anything specific on this. However, I don't think it would make much difference if you start with warm water, it will soon be cool and the unit does not put out that much mist to feel warm. I do use distilled water as I saw in other posts on other units that that was preferred.
You can use it with just water. But then it would just put moisture in the air, if that what you want then just get dehumidifier. This is for oil diffuser, with a drop of oil, with 100 mL of water. It would last up to 6-7 hours. I hope this help.