As it happens, most wines (the ~95%) aren’t meant to age, so you’ll discover that finding an age-worthy wine is a bit more challenging; almost akin to finding well-made clothes. So here are the primary traits of age-worthy wines.
Wines with structure
Finding wines that will improve over time requires that you pay attention to a wine’s structure. What is structure? It’s the taste attributes found in wine that act as natural preservatives:
Acidity - Wines lose acidity over time, so it’s important that the acidity be moderately high.
Polyphenols (tannin) - The polyphenols in wine stabilize things like color and flavor. Thus, wines with moderate tannin (from both oak or grape) have a longer runway to age.
Sweetness - Sugars have been used as a fruit preservative (jam) for a very long time. The same ideology behind fruit preserves also applies to dessert wines and wines with high sweetness levels.
Alcohol level - Alcohol is one of the primary catalysts that causes wine to break down. Strangely enough, it also acts as a stabilizer in higher amounts (e.g. fortified wines and some dry wines with >15%+ ABV). So you either want lower balanced alcohol levels or high alcohol levels.
Low volatile acidity - Acetic acid is detrimental to age-worthiness in wine. Avoid wines with VA levels around 0.6 g/L and above.
Balance
After structure, look at balance. Are all the attributes of the wine in balance with one another? If a wine has tons of tannin, acidity and moderate alcohol (maybe around 12%–13.5% ABV) but has no fruit then it’s not really in balance.
Producer
Who made the wine? Before buying, look into the producer’s history. Ideally, grapes are grown on the producer’s estate and the winery has a track record of solid winemaking for 15+ vintages. Of course, there are many well-made age worthy wines made by producers who don’t fit this profile (and vice versa), so don’t let this alone deter you. The biggest red flags for producers would be inexperienced winemakers who don’t have a scientific understanding of enology at the helm. These wines are no problem upon release but subtle flaws will become exacerbated with age. Another deterrent would be white label wine brands; these wines are usually made to drink now and will not increase in value.