The only time I use the AUTO setting is on the very hottest summer days. Set the temp to 72, hit AUTO, and the let the climate control keep the car cool inside. But as soon as the sun goes down the whole thing is turned off and I roll the windows down!
Honestly, I need to buy a spare climate control unit as well. I am not worried about it failing to function as much as I am about the LCD panel 'bleeding' or going out completely.