Somebody turns forty and the obvious present is a bottle from the year they were born. The difficulty is that the year is fixed and everything else about the wine has to bend around it, including whether that vintage was any good and whether anything from it is still alive.
The year is the hardest possible constraint
Normally you choose a wine and take the vintage that is available. Here you choose the vintage and take what exists. If that year was poor in a region, no amount of money fixes it, and a great producer in a bad year is still selling you a bad year.
Aging depends on structure: the tannin, acid, sugar and alcohol that let a wine develop slowly rather than fade, as Decanter describes. Most wine never had that structure and was not meant to. Start by asking which categories are still standing, then check whether the year was kind to them.
What survives twenty to forty years
Madeira: effectively indestructible, decades to a century Vintage port: very long lived, and dated by definition Sauternes and other sweet wines: decades in good years Classed Bordeaux, Barolo, Rioja Gran Reserva: decades in good vintages Vintage Champagne: long lived, condition permitting Everyday red and white: almost never
For a difficult year, fortified wine is the reliable answer. Madeira in particular is made in a way that shrugs off both age and imperfect storage, which makes it the most reliable old bottle to buy and the one most likely to still be enjoyable when it is opened.
Buy the condition, not the year
An old bottle is worth what its storage history is worth. Ask for the fill level and a photograph, ask where it has been kept, and be skeptical of listings that describe the wine at length and the bottle not at all. Fill level is the best clue available when nobody can prove the storage, as covered in the auction guide, and the inherited collection guide covers reading capsules and labels the same way.
Buy from a merchant or auction house that specializes in older vintages rather than the cheapest listing you can find. Expect to pay for provenance. That premium is the actual product.
If the vintage was poor
There are three honest ways out. Choose a category that is less vintage-dependent, such as Madeira or a tawny with an indicated age. Give a wine bottled in that year rather than grown in it, which fortified styles allow. Or change the gift entirely: a young bottle from a great recent vintage, bought to be opened on a future birthday, is often a better present than a tired bottle from the right year.
If it is going to be kept for years, say so on the card and make sure the recipient has somewhere to put it, as the gift guide covers.
Opening it, when the day comes
Stand the bottle upright for a couple of days, expect a fragile cork, and have a backup bottle in the room. The decanting guide covers pouring off sediment and why an old wine may want minutes of air rather than hours, and the opening guide covers a cork that crumbles.
Then write down what it was like, even if the answer is that it had faded. A forty year old bottle is a piece of history whether or not it is a good drink, and the note is the part that lasts.