Unlike wine, the majority of beers are not brewed to age. Beer typically spoils within a few months, a year at most, with rare exceptions. Even specialty brews aren't made to improve over the five, ten or even longer age of some fine wines. There are some specialty brews, though, that can age up to 30 years.
Here are some tips for home brewers and beer drinkers to keep that great bottle in premium shape until you can no longer resist opening it.
Tip #1: Drink it all. If you didn't resist opening that bottle, but found yourself satisfied halfway through, don't put the remainder back into the refrigerator for long. Even if well-sealed so it doesn't lose carbonation, air will continue to react with what's left, leaving it unworthy after a few hours.
Tip #2: Stopper well. Since air is one of the main enemies of a good brew, it's ironic that nitrogen -which makes up 79% of normal air- should be used in kegs and some cans or bottles. Small nitrogen-containing pellets, called widgets, are used in some applications. The gas flows out a small pinhole when the container is opened, helping to create a nice, foamy head.
Natural cork does a good job of sealing bottles, but modern plastic derivatives are much better, even if less stylish. No need to store the bottle horizontally, though. Cork-drying isn't a problem under normal circumstances. Just make sure the cork is inserted a half-inch or more and doesn't contain any obvious holes or mold. It's the oxygen in air that does the damage, along with organisms in the air.
Storing upright also allows any remaining yeast to migrate to the bottom, where it's more easily filtered out. Bottles stored on their sides cause yeast not only to accumulate near the cork, but also to scatter when the bottle is tipped upright for uncorking. Unless you happen to like the more 'complex' flavor imparted, keep it upright.
Tip #3: Keep it in the dark. Unlike your spouse, your beer should not be let in on your plans for it. Keeping it in a low-light area will help to combat the second major cause of beer spoilage: ultraviolet light exposure. A condition sometimes called 'skunked'.
Chemically, for those interested, 3-methylbut-2-ene-1-thiol - a constituent of skunk spray - is created, leading to the distinctive odor and taste.
Any visible light can harm beer, but the invisible ultraviolet is more energetic and causes several components in the brew to break down and combine with other compounds. The products of that reaction are always less tasty than the original. It's not called skunked for nothing.
Tip #4: Keep it cool, not frozen. Like most food products, beer benefits from low temperatures. But freezing beer forms ice crystals that don't melt back exactly the way they were initially. The result is usually lifeless and unappetizing beer.
Some strong brews, like Trippel or Barley Wine, store well at a few degrees below room temperature, 55°F-60°F (12.8°C-15.5°C). Most ales - Bitter, Dobblebock, Stout and others - will benefit from cooler, cellar temperatures, in the range of 50°F-55°F (10°C-12.8°C). Lagers and other lighter beers do best in colder conditions, around 45°F-50°F (7.2°C-10°C).
But, not everyone has an area suitable for storing beer, nor can afford a specialized refrigerator. If you can't maintain the light and temperature conditions needed to store beer, there's really only one good alternative: give in to that temptation soon.