As they say your mileage may vary (and I really do hope to avoid gloating even implicitly) but ten minutes ago I opened a square tin of Penzance bought new for about $8 at the Davidoff shop on Madison Avenue in 2007. It's been at a stable temperature in the dark undisturbed ever since.
As I hoped, the seal gave with the twist of a coin. Aside from the tissue paper lining going jet black, the contents are magnificent, the moisture level perfect, and it smells glorious.
Storing wine for long periods faces so many of the same issues--corks are flawed from the get go or dry out; a bottle sits in a container baking on a dock for a few days after being landed in Texas at the height of summer; a store displays it under florescent light for six months; the owner moves house and his wine cellar a few times. And all else.
In that world, accordingly, prices quite often reflect at least some plausible guesswork about how good a particular bottle's history has been--from hints like ullage. And top dollar is often commanded by bottles that it is known remained at the chateau from the day they were bottled until placed at auction, or in the cellars of a major negociants who bought them upon release. As for a plastic pouch of Balkan Sobranie with a health warning printed in Italian being sold by someone in Germany on Ebay now--not exactly the same thing.
I am sure I've been lucky this time (and am grateful). If only I'd had a crystal ball and bought a few dozen more. And not just this one.
I know that both Greg Pease and Jesse know what they are talking about, and I've no doubt the physics of square tins vs round ones, and coin twists vs pop tops, has some relevance to the calculus. But all the tins of 15-20 year old tobacco I've opened this year have been fine. I expect I may open a dud at some point, but at least I actually know how they've been stored for most of the time. Indeed, if not everyone, I suspect many who cellar now are betting heavily on their favorites being in really sound shape long beyond seven years or 2027. But yes, mylar tape sounds like fun.