The correct answer is B. drastically reduced.
Insulating materials are designed to withstand a certain amount of heat. If they are operated beyond the maximum allowable temperature, they will start to break down and their lifespan will be drastically reduced. This is because the heat will cause the material to degrade, and it will eventually become too weak to function properly.
Option A is incorrect because operating an insulating material beyond the maximum allowable temperature will not increase its lifespan. In fact, it will do the opposite.
Option C is incorrect because operating an insulating material beyond the maximum allowable temperature will affect its lifespan. It will not be unaffected.
Option D is incorrect because the correct answer is B.