Let's say I have a large mason jar of an aged blend (5 years +) that I open very infrequently (couple times a year) and consume over many years, would it be better for my smoking enjoyment to have that large jar split into a bunch of smaller jars to prevent accelrated degredation of the tobaco at the bottom of the jar?
This will probably set someone off, but if you are opening the jar, you are not aging that tobacco, not in the sense that someone who cellars is. If you are dipping into the jar, you are merely looking to smoke that tobacco over a long term. It may change, but not in the same way.
A 5+ year old tobacco probably isn't going to turn to shit on you as fast as I am talking about above.
Recently, a guy who scored a 20+ Escudo, got it into a jar as soon as he got it, smoked a few bowls of it over the course of a week or so, but wanted to share it with a few of us in the pipe club. When we smoked it, it was shit. He was all, "I don't understand. It tasted fantastic." But, by the time we got to it, it had lost all of its oils, because he had waited so long and had been dipping into it.
I know that some guys have 100's of jars that they smoke out of, and that is great. But, in my experience, when you deal with a really old tobacco (20-30-60 years old), once you pop that seal, the clock starts ticking. How long aged, what you do with it after breaking into it, how long after you disturb that microcosm going on inside that jar which is no longer full of ambient oxygen, are all variables. So many variables. I just would suggest approaching a really old vintage tobacco a little differently that one that you've just bought. Maybe it will last weeks of smoking, maybe not. I just wouldn't want to be "that guy" who is left with a jar of crap because they wanted to try and stretch out how long they can smoke it.
But, if we are just talking 5+ tobaccos, I have yet to run into one under 20 that turned to shit. However, if you are dipping into it... your chance of losing all of those oils by stretching that jar out over a year is greater.
Me, when I get hold of a really old tobacco, I wait till some friends are over, and pop that thing with a bottle of wine, and just enjoy the hell out of it till it is gone. But, if we are talking just 5 years, you're pretty safe.
For me, it is just about setting up safe practices. How will I mitigate... by expecting the worst case and taking measures to prevent. Otherwise, just do it your way.