Recently I posted about being careful about multiday race challenges such as the goofy and dopey marathon challenges. Here is some new science behind recovery in a study done by the American Physiatry Journal. The study concluded that instead of the typical 48-72 recover period for middle and long distance running events 5-7 days recovery was optimum after participating in multiday running challenges.
https://www.sciencedaily.com/releases/2016/02/160218062221.htm