It has been said that cork helps wine age because it has just the right amount of oxygen permeability. Just enough air gets through to help the wine age gracefully. However, recent research indicates that this may not be true, and that screw caps actually do better at preserving wine. Take a look at our article here:
http://www.winemcgee.com/blog/2010/01/19/the-state-of-the-cork-what-is-the-best-wine-bottle-closure/