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.
It's essential to sleep in most multiday races. The body cannot go much more than 36 hours without losing a serious amount of mental clarity. The art of multiday running is discovering how much sleep you can get away with. There's a fine line beyond which the body needs a break. If you are uninjured yet averaging less than 3 miles an hour in a session, one should contemplate a break. Under extreme exhaustion its not always easy to make that decision for oneself. Hence one of the advantages of having a handler who is able to assess your situation from a clearer perspective.
How Much Sleep
The amount of sleep necessary will of course be different for everybody. Some people may prefer 2 or even 3 sessions spread throughout the day. Generally there is a trend of thinking that sees a minimum of three hours and with another REM cycle thrown in, maybe four and a half hours is ideal. For races longer than 10 days perhaps a little more would help recoup energy levels and aid recovery. The runners in the Self-Transcendence 3100 mile race rest between midnight and six in the morning as the course is closed at that time. That leaves about five hours of actual sleep.