[ngnichols]

A BGS/BVG card has an internal sleeve that the card is put into before it even goes into it's outer holder. This removes any air/moisture exposure that would cause any additional deterioration of a card so long as it goes in dry and without mold already on it.

Their outer holder also has a UV protective coating that will prevent fading of both cards and autographs. That being said, it's still not a good idea to store your cards in direct sunlight for extended periods of time and/or fluorescent lighting.