title_body: How fast do I need to finish a Hefe Weissbier Keg?
upvoted_answer: Where did you read this? I am unfamiliar with Dunkle Hefe exactly, but this is true for wooden casks. 
  Typically a wooden cask is served with gravity or with a hand pump to lift from a cellar. There is an opening in the top that draws air in to equalise the pressure. This air will reduce the shelf life to 3 days.
  A "Donkey Pump" on the common sankey keg is similar. The beer will spoil quite fast.