The thing is, this would just be equivalent to leaving it on at all hours, because who would join such a chat room without the intention of switching it on. Even if you joined such a chat room and had some restraint and decided to wait till the moment you thought would be most amusing, someone else would definitely just decided that it should be on now and basically the only lull would be if the number of users was relatively limited and mostly in the same timezone so everyone is sleeping.