Allowing your red wine to breathe is a useful trick that assists in releasing the aromas as well as smoothing the rough edges. Tannic and young red wines such as Left Bank Cabernet Sauvignon-based Bordeaux and Syrah or GSM blends from the Rhone Valley can benefit from being left to breathe because it softens their tannins, but the amount of time you should leave a wine for varies as well as how you aerate it. Just opening the bottle doesn’t necessary do much to the wine – it’s much more useful to decant it into another vessel and for some added theatre, pour it from a height!
The older the wine, the more delicate it is. Aromas and flavours can lose their strength quite quickly in an aged red wine, so the length of decanting (or any at all) won’t always be necessary. If your wine is over 10 years old, pour yourself a glass to see if it needs to breathe. If your red wine is young with chunky tannins, letting the wine breath for about 1 to 2 hours will reduce any harshness and bring out a more velvet-like texture. If your bottle is a lighter wine, or less alcoholic or concentrated in flavour, 30 minutes of breathing time should be ample.