Will bottle aging help subdue the "hot" taste to a wine with a high alcohol content?
Answer From Expert Roger Bohmrich MW
It is generally believed that the alcohol content of wine remains the same as it was at the time of bottling as the wine ages. However, chemical studies of very old wines are scarce given the inherent difficulties associated with controlled experiments which last for decades. Some wineries which have relatively large stocks of old bottled wines (La Rioja Alta in Spain, for example) have found that the alcohol content drops by about 1% after 15 years of bottle age, presumably from transmission through and/or around the cork. Coming back to your question, it may well be that a wine that tastes "hot" is fundamentally imbalanced and will not improve with time. On the other hand, thinking of Vintage Port as a noteworthy example, the intensity of the alcohol seems to diminish with long aging (2 or 3 decades). This suggests that the overall aging process is more influential than the chemical changes of any one component.
