Wine ages as air moves in and out of the cork, interacting with the flavor components of a wine. With large format bottles, you’ve got the same surface area for air transfer — that tiny cork — but a much larger volume of wine. The result is that these bottles age at half the speed of their 750 ml counterparts.
It’s because of this aging potential that many top-notch wines are bottled in large formats. Big bottles age more gracefully and just plain better, according to some experts, because they age at a slower pace. As a result, producers typically bottle a portion of their best blends into large bottles to see their evolution, and mark them up accordingly for collectors.