This is a great idea. I have another suggestion because the back of my mind has me worried that if somehow the timer malfunctioned and stayed on, then the mister would stay on constantly too.
So an alternative setting would be to set the timer so that it turns on every day but only during the day, i.e. 10am to 4pm. And then you set your mister to the setting that you want, i.e. 45 seconds every 2 hours. With the example setting I described, the mister would turn on at 10am for 45 seconds, at 12noon for 45 seconds, at 2pm for 45 seconds (but I am not sure about the 4pm for 45 seconds because the timer would turn it off so maybe set the timer to turn off at 4:02pm instead of 4pm). This way, if the timer malfunctions, at least the mister will only turn on every two hours for 45 seconds each interval. Does this make sense? If not, I will try to explain in a different way.