Aging beer can have a number of benefits if done correctly and with the right type of beer. It can bring out different flavors in beer, such as bread flavors, earthy notes, and woody or metallic flavors. It also tends to reduce the bitterness of beer, as hops lose some of their potency over time. If after the next “taste test” it doesn't taste as good as the previous time, then it's time to drink those beers.
As is the case with wines worthy of aging, beers that are destined to be beautiful after 10 years or more of bottle-aging will tend to first experience a tough, expressionless and disconnected youth. And wild beers, or beers fermented not only with traditional yeast, but also with certain microbes associated with wild beer styles (lactobacilli, pediococcus, brettanomyces) are more likely to improve or evolve with age. Beers that age well tend to have relatively high hop bitterness, but have more malt than hop aromas. Although it is not always true that darker beers age better than paler beers, this is often the case, with notable exceptions such as the lambic varieties and some Belgian triples.
Aging wine bottles on their sides prevents the corks from drying out and shrinking, but this is not usually a problem for beer, since most beers are sealed with a crown-shaped lid or a compressed champagne-type cork. In addition, since different people prefer different flavors, some may actually enjoy the taste of aged beer, while others may find it unpleasant. The most important thing to remember is that taste is subjective and, in the end, aging beer depends on personal preferences. While most beer throughout history has been destined to be consumed in a matter of days, weeks, or a few months, certain types of beer have always been destined to age even more.
What happens is that strong flavors tend to decrease and the more discrete flavors and characteristics of beer occur as the beer ages. Lambic beers and similar beers have probably been brewed for more than 1000 years and are traditionally aged in oak barrels. In fact, all beer can be “aged” (or, in fact, stored) for a few months (longer if kept under the right conditions). For example, a stout can taste great after just 6 months, while a sour beer can take a year before those fruity flavor notes really shine.
It was discovered that the 137-year-old beer was in an amazingly wonderful state and reminded tasters of a good old amontillado. Although barley wines and imperial dark beers aged for 10 or 20 years are not unusual, some beers have considerably longer lifespan.