Decanting Wine - Interior Crew Matters
Wines have all sorts of organic things in them - yeast, grape skins, and so on. The wine naturally has very small particles of these things that, over the years that wine age, settle out of the wine. That's why with older red wines, which have much more skin contact, you get more sediment.

Why and How to Decant Wine
Three Reasons for Decanting Wine

- Old wines that have been cellared properly will contain sediment due to the aging process. By properly decanting the wine, the sediment will remain in the bottle.

- Young full-bodied red wines can benefit from decanting. When the wine comes in contact with oxygen, the aromas present in the wine are released. The decanter in this case should be a wide bottomed decanter. Wide body decanters provide more surface area for oxygen to allow aromas from the wine to be released.

- The presentation of wine in a beautiful crystal decanter adds to the ambience of a beautifully set table and prepared dinner.

How to Decant Aged Wine

- For old wines with sediment one needs to be very diligent about pouring the wine into a decanter. First, stand the bottle up for several hours to allow the sediment to settle at the bottom. Fine sediment will take longer to settle to the bottom of the bottle.

- Use a lit candle or lamp. Hold the bottle of wine so that the area just below the neck of the wine bottle can be seen through the light while pouring. Ever so slowly begin pouring the aged wine into the decanter. Be patient. Hold the bottle as much as possible perpendicular to the candle. As the last one-third of the wine is poured, carefully watch for sediment. Stop pouring when any sediment appears in the neck of the bottle.

How to Decant Young Red Wine

- For young red wines, splash the wine into the decanter. The more it splashes into the decanter, the more it comes in contact with oxygen. Let the wine settle and rest for a short time.

Remember that your tongue can only taste four types of tastes.
All of the other sensations you get from wine come from your nose. You want that wine to be giving off aromas! If it's not releasing flavors into the air, it's going to taste like strange water.
You can usually let the wine sit in the decanter for 1/2 to 1 hour before you drink it. You'll see how its flavor changes over the evening as you drink.

The primary reason you keep wine bottles on their side during storage is so the cork stays wet.

So it doesn't dry out and let in air. You're doing the opposite here. You are trying to expose as much air as you can to the wine, during the hour or two you are decanting it.
So this has nothing to do with long term storage or wet corks. It solely has to do with wine sitting in a decanter, interacting with the air.
The decanter is meant to do that in its normal position.