This is not one IT officer's opinion, this is a conclusion from empirical modeling. Why do we have traffic rules of speed limit? Why do we not have different speed limit rules for different small cars?
Speed limits are about safety, not about the longevity of the vehicle.
Are you seriously saying that no matter what type of materials are used in the manufacture of a graphics card that if you go over 70c then the lifespan of that card is reduced by 50%?