From the Magnum and beyond, the conservation of aromas associated with winemaking and barrel ageing as well as maturing ability of the wine are multiplied. This calculation is proportional to the size of the bottles: for example, a Magnum’s ageing potential is multiplied by two, the double-Magnum by four, that of Jeroboam by six, and so on.
This can be explained by the fact that wine, in large format, suffers less oxygenation: the proportion of air in between the cork and the wine is less than in a 75 cl bottle. Therefore, any changes will occur more slowly. Moreover, the bottle’s thermal inertia is greater, meaning that a large format will be less sensitive to the temperature variations it may have to experience along its lifetime.
Generally speaking, it is recommended to open your large formats two to three hours before serving, depending on the potential of the vintage and its age. Avoid opening a great vintage too close to serving time when in a large format, as the concentration of the wine would not allow you to appreciate its true quality. Conversely, if the wine has reached a very advanced state of maturity, the surface of the wine in contact with air during the service being much larger in big bottles, opening a bottle too far in advance will cause some of the more subtle characteristics of the wine to dissipate.