I think it depends on where you live and/or where the humidor will be. I'm in SoCal and don't get the kind of temp. swings that some see, and my Aristocrat is in a cool room at the back of the house. I don't have the temp. control unit and can't see buying it for what might only be a 5-10 day stretch during an occasional really hot summer (plus I have a closet that never gets over about 65° where I can park the humidor). That being said, I'm so impressed with every product I've gotten from, and every conversation I've had with Bob, added to the glowing reviews on his temp. control system, if I needed one I wouldn't hesitate to buy it.
(hope you're not an english/grammar teacher).