Assuming you are using this to heat strike/sparge water you shouldn't be cycling that frequently. That unit has a minimum 0.5C hysteresis on it. Assuming you have at least 4 gallons in the pot it will take a few minutes for the water to cool that much. If you were concerned about it you could up the hysteresis term to 1-2C, but I would just leave it and see how often it cycles. With regards to wether the probe can handle boiling temp, just pull the probe out, you're going to want the element on full bore anyway, your boiling wort is going to be at 100C, probe no longer necessary. Having said all that, have you checked the current rating of the unit vs. your element. If memory serves it is rated at 10A, but I never payed that much attention as I'm only switching a 1.5A device. Any more than that and you'll want an external relay. Sparkfun.com has (had at least) an extension cord rated at 15A with a built in relay that triggers off of 5V that I think is cheaper than all the components separately. That and a wall wort switched by your STC and you'd be all set.