Much is made of the age of wines, but laymen and amateur wine collectors often do not understand the specific requirements to allow wine to age correctly. Kosher wine is a complicated combination of patient distillation and natural maturation. Knowing exactly how to influence those factors is what makes the best winemakers and it keeps the best collectors in fine wines for ages.
A wine's ability to age has quite a few mitigating factors, but all most all of them come down to one simple, bite sized ingredient: the grapes. The grapes used in a wine are its essence, its reason for being, and the primary root of its quality. Growing grapes is a complex process, and the magic of Mother Nature has made it so each variation on growing or, viticultural practices as the experts call it, can alter the grape greatly. This means soil, region, water source, allowance of sunlight and more can alter a wine and its ability to appreciate with age quite severely.
Though it is nearly impossible to know how long people have understood the relative quality differences in properly aged wines, it is clear that the Ancient Greeks and Romans were very keyed into these properties. The dried "straw wines" of Ancient Greece were noted for their ability to age well, thanks in no small part to a very high sugar content. Some Greek philosophers even spoke of the quality of aged wines in their texts and dialogues. They also suggested heating up wines to artificially age their favorite reds and whites, but also warned that this seemed less healthy than naturally aged wines.
After the fall of the Roman Empire, there was a notable dip in quality wine production. It resulted in lighter colored wines that would turn to vinegar in just a few months time. It was not until the 16th century that Mediterranean wines once again started to gain notoriety for their ability to age. The key was that higher alcohol content acted as a preservative in wines, as it would from then on.
Still, many worry that wine drinkers the world over are being sold snake oil when it comes to aging wines. In particular, the British wine critic and supposed "Master of Wines" Jancis Robinson estimates that only the top 10% of red and 5% of white wines have the ability to improve with age. What's more, he has said only about one percent of each of those show the ability to significantly improve after a decade.
This all points in one clear direction, your wine bar. While some of those kosher wines might be good to keep on hold for a while, buying wine online and cracking open a bottle is probably not going to make your future wine consumption any better or worse for the wear. It is interesting knowing that wine is among the only consumer goods that can truly get better with age. Your pallet is surely thankful for that as well.