This article by Dan Selakovich makes the strong case for why films benefit from a skilled editor, separate from the director: http://www.watchindie.net/2015/10/27/why-a-director-shouldnt-edit-their-own-movie/ It boils down to objectivity, to getting away from all the baggage of remembering what happened on set.  He makes a compelling case, and his advice is the conventional wisdom.  It reminds me of WIlliam…