Pacing is a vital component of a multiday race. Many experienced ultrarunners have come unstuck by running too fast on the first day of a multiday event or even within the first few hours. This is not a problem confined to multiday runners - everybody can have this experience at any distance. What makes it more significant here though is the fact that red-lining the leg muscles without appropriate conditioning on day one can make day 2 extremely painful yielding relatively few miles. On the other hand going out too conservatively is missing the opportunity to make the most of fresh legs.
Breaking the event into smaller chunks imposes a structure that can aid in maintaining a rhythm.
Strange as it may sound but taking breaks is an essential part of the overall strategy. How you break the day up is a personal choice depending on the amount of mileage that needs to be covered and the size of the window available to reach that target.