It's not the matt that malfunctions, it's the thermostat controlling it. Some run wide-open when they fail, others shut off.
VE's are notorious for running wide-open when they fail. A dimmer switch between the t-stat and the appliance set so that the appliance maxes out in the upper 90's if there is no t-stat in the circuit will help ensure that while your snake may be uncomfortably warm for a while, it doesn't get badly burned.