You’re asking a very good question and you’ve received some equally good responses.
There are a lot of variables, and as those variables increase over time the results become more variable as well.
Even with everything seemingly the same, results can differ. I’ll offer an example.
About 13 years ago I split up a box of Gawith FVF into 3 mason jars for aging. All three jars were new, from the same palette. The jars were packed and sealed in about a minute. They were stored side by side on the same shelf for 8 years.
They all came out differently. The tobacco in one jar developed a wonderful caramel like sweetness. One jar had a less pronounced sweetness. The tobacco in the third jar was flat. All of the jars were equally well sealed, they were from the same batch, they shared the same environment. All different.
Different blends change differently as time goes by. Different components change differently as time goes by.
Different versions of a blend, made by different manufacturers, change differently.
It’s all a bit of a crapshoot.
The oldest blend I’ve smoked was about 100 years old and it was absolutely vile. Tasted like what I would imagine zombie vomit would taste like.
The majority of the blends I’ve tried above 50 years of age were compromised, very much reduced, more like wraiths. That said, the occasional tin will defy the odds and be truly fine.
But, the odds get slimmer as the years go by.