The "Pre" is the Meeting of the Host with snacks and Drinks optional. Dependent on the arrival of the most important Guests and the Caterers it can be a short or long time, Is the food being spoiled a greater concern than the Guest of Honour running late. Before Weddings Meals it is the Photographer that might have the Bride and Groom delayed
The afters, Business, Civic and Corporate functions is Speech time and that can go on an awful long time. Dependent on your Guest status {Ranking} you might avoid leaving early but if at the bottom of the Boss's table your disappearance might not be rewarded, if noticed.
The Afters after Weddings, Family Parties and a Few Corporate events are Where the Hair is let down and the normal enjoyment begins, The reward for sitting through a stuffy Dinner.
How long till the last Guest leaves chased by the cleaners means a good night was had by some.
Not all Dinners that are Formal need to be escaped, things can be terrific it just depends so much on the people you are sitting and mixing with and how quickly you relax. Great food and just enough drink helps but lives have been ruined by too much, Pre or After
