Tasting the same wine over time, aside from being fun, is one of the most educational things a wine lover can do. It gives you greater respect for wine in general and a deeper knowledge of the individual wine, and it leads to a better understanding of the entire concept of aging wine. Generally, even inexpensive reds, so long as they are well made, benefit from a year or two in the bottle. To keep, and to improve in keeping, a red wine needs certain elements. These are fruit, acid, and tannins and most important of all the balance between them.
Good fruit is the basis of any good wine.
Equally important is some acidity the sharpness usually perceived at the tip of the tongue to keep the fruit from feeling flabby or mushy. Acidity also preserves the freshness and allows the wine to keep. Tannins, derived mostly from the skin and stems, but also from the barrel in which the wine is aged, provide the backbone for aging. Tannins are generally perceived as the mouth-coating, sometimes puckering dryness on the palate and especially on the finish of a wine. Time hopefully tames these tannins, thus rounding the rough edges of a young wine and bringing the component parts into a more harmonious whole.