Many experienced homebrewers leave their beer in the fermenter for 3-4 weeks. Beginners find this very difficult to do. But here's a real motivator: when a batch is done fermenting there will be a layer of trub. By waiting an extra week or two, this layer will compact leaving you with an additional 2-3 quarts of clear brew.
That's most of a six-pack.
That's most of a six-pack.