I liked having a thermometer when I was first learning. I agree that they are not necessary in a pot still. I have one on mine so I can stop the stripping run at a certan temp at a glance, but that can be done by other methods (taste, smell, alcoholometer, ect.).
7 1/2 gallon (30L) stainless steel pony keg boiler
12 inch copper packed column 1 1/2 inch diameter
3 feet of 1/2 inch jacketed with 2 feet of 1 inch condenser