Always a good question. In 2019 I bought 17" Michelins from a large online retail tire store and they were all already 1 to 1.5 years old. I'm sure probably due to the big gaps in production runs and the low turnover in these 17" Michelins.
To try to deal with the tire issues and make them last longer, I keep my cars and tires in the basement where it's always around 70 degrees, no sunlight, no ozone (keep away from the HVAC equipment).. and try to drive them at least every other month or so to keep the rubber compounds moving around and supple. It is still a losing battle over time.
After 30+ years of Michelin 17" PS2s, I've found that I get about the same number of miles out of the fronts regardless of how hard or easy I drive.. if no flat spotting. The rears are a different story.
I once bought several rears and put them in the basement and when I finally got around to needing them, they were over 6 years old at that point. You can't win for losing if tire age is a big concern to you. It is what it is.
