Agree, expensive doesn’t automatically mean delicious. So many factors affect how a wine turns out.
That said, when it comes to aging, it really depends on the wine. I want to drink something like Torrontes or Beaujolais Nouveau as young as possible. Those wines are made to be fresh and aromatic, if you age them, they lose the very things that make them special.
On the other hand, I prefer a Rutherford Cabernet around 10 years old, and a highend Bordeaux closer to the 15-year mark. Beyond that, I know I’m rolling the dice… unless it’s Vintage Port. I’ve been lucky, I’ve never had a bad old bottle of vintage Port.
Homemade wine is its own challenge. I homebrew, and outside of mead, most of it needs to be drunk young because it gets a lot of oxygen exposure during the process. That said, I do have some 10 year old homebrew that’s still very drinkable, but only because I fortified it with whiskey. At around 20% ABV it’s powerful, fun and give you a lovely buzz, though a wine expert might find it a bit unbalanced.
As for why I buy expensive bottles? Mostly because I drink them with groups. Those tastings end up being about a lot more than just the wine, we build real rapport, network, and form lasting friendships.