ASIDE FROM THE QUALITY OF THE GRAPES AND THE SKILL OF THE WINEMAKER, WINE QUALITY WAS VERY DEPENDENT UPON THE AMOUNT OF TIME IT WAS GIVEN TO AGE.  FIRST, LET'S CONSIDER HOW WINE VARIES IN QUALITY:

Wine Quality

Long ago, people recognized that wine varied in quality and thus prized the best wine.

Here's an example of the worst wine - not only was it "sour", but probably "acetified", or in other words, vinegar.

The highest quality fermentable juice was produced by the least pressure, which was simply by the weight of the grapes themselves when piled in heaps.  This "first run" juice was carefully separated from that juice obtained under heavy pressure. The lowest grade (probably for making vinegar) was made by adding water to the pressed solids prior to fermentation.

Aging

Probably by accident, winemakers long ago discovered that wine would improve in quality over time if properly cared for.  In fact, after 40 days, it was offically considered wine suitable for a "drink offering".

Why is "wine on the lees" the finest aged wine?  (Remember, we saw in "racking" that wine should be transferred off the lees). Normally wine that has lees on the bottom of the wine vat is considered unfinished - if the wine is not racked, the lees will eventually impart off-flavors to the wine.  Certain kinds were left undisturbed to age "on their lees" and were thought to be all the better for so doing, but before they were used it was necessary to strain them very carefully. So Isaiah 25:6, `A feast of wine aged on the lees, thoroughly strained.’ But usually leaving the wine in the fermentation vessels interfered with its improvement or caused it to degenerate.

Because of the harsh conditions in Palestine and the lack of preservatives, "old wine" was any wine stored more than one year, and three years was the maximum any wine could be kept.

This verse really sums it up - that is why old wines are more expensive than new wines!