How long is a piece of string? There is no definitive answer.
Of course, most of the wines you buy will be for everyday drinking and you don’t need to worry about drink dates. If your wine is designed to be matured, the best way to find out is by tasting it. If you don’t want to be disappointed, the best thing is to consult a drinking dates guide – you can find them on decanter.com or in Hugh Johnson’s annual pocket wine book.