If the shot was less-than-perfect or marginal, it' s sometimes best to leave them overnight. I' ve done it (as have a number of hunting friends) on numerous occasions--even early in the season with never a problem due to meat spoilage. I have had other predators get to my deer before I did--on consecutive nights in two different locations. I lost the entire hindquarters of one deer and the tail and a little bit more of the only piebald deer (98% white) deer I' ve ever harvested.