Cutter tops were the bomb. Blends could keep for decades in those. Round screw down tins are not as robust, but about the best we have these days, and those can last a few decades though some will fail. Square and rectangular tins start getting iffy within a decade. Some hold their seal for much longer and others will have failed long before that milestone is reached. Sealed jars are a time honored method for long term storage, though some will fail, and Mylar bagging is becoming more widely recognized as a fully acceptable alternative.
Climate and temperature play a role, though not as much as people think. I've jarred contents from a bulk purchase into a number of jars at the same time, sealed them at the same time, and stored them next to each other for a decade, and had the contents age differently from one jar to another.
As your tobaccos age, they will change, more or less. Maybe that change will be an improvement for you, maybe not. Latakia may start to lose strength after a few years, though I've had vibrant Latakia that was 30 + years old. It's all unpredictable. That's also part of the reality of cellaring.
In short, cellaring is a bit of a crap shoot, but there's no alternative if you want to have stock of your favorite blends available to you when you want them.
