from Kerry Fraser of TSN,

There should be no reason (in the two-ref system) where physical fatigue might negatively impact the decision making process for an official regardless how many overtime periods are played. The mental aspect of a referee's performance is a whole different kettle of fish! While players don't want to become the "goat" by making a bad play or mistake, the referees' internal struggle is all about rendering a decision that might be perceived as a game ending bad call. (You notice I said perceived.) The best remedy in dealing with this pressure is for the official to maintain a rock solid focus of concentration by remaining in the moment and react to call penalties whenever they occur. Once a ref stops refereeing and puts his whistle away he becomes a spectator instead of an enforcer of the playing rules.

Each referee can feel intense pressure to make sure any call he makes is viewed as a "must call" in the late stages and overtime. The referees' best work is done well in advance of the late stages of a game by maintaining the expected standard of enforcement and to keep the players in check throughout the entire game. The best deterrent against infractions being committed is "fear" a ref can instill in players that he will call the penalty whenever it is committed.

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