Other then three faulty switches in a row, you may be wise to do a little more checking for another problem that's causing the switches to fry.
Corrosion in the wires, motor starting to go south, could easily cause excessive resistance and overheat the switch. Like said, you run on 3rd speed most of the time, so it would be more prone to showing the fault. But just as easily, if something else is the actual cause of the problem, you could see the same results if you ran the blower on 1/2/4 all the time.
97 Sahara, 74 Renegade, 72 CJ5, 55 Willy's (the Beast) Boss 302, 6:34 gearing, Bose 901 speakers.
God I miss that Jeep. Forgot the kinda Jeep, 80 SX4.