What is meant by "length"?

Wines where the flavor lingers in the mouth after swallowing are called long, and this is considered to be a positive description: the intensity and persistence of flavor reflect the quality of the wine. The aroma and flavor continuing in the mouth after the wine has been swallowed is called its aftertaste: the quality and enjoyment of a wine's aftertaste, combined with how long it lingers, is described as its finish. The finish can sometimes give an indication of how a wine might age: poor wine invariably produces an unexciting end.