From what I've read, aros are meant to be smoked without aging. In fact, many claim there's no real aging taking place with aros (as opposed to VAs). As well, generally speaking, if an aro is well sealed and jarred, it will still smoke well years later.
The only aromatic that has improved with aging in my experience is Peterson's University Flake - and it's not really a "true" aromatic, but a VA flake with a nice plum topping. A properly stored aromatic probably won't get any better, but shouldn't get any worse, either.
They don't really age much. The most that will happen is the flavor will dilute. I only smoke aros though and have a few blends that have been sitting in jars getting occasional rotation for going on a year now they're still pretty good. Like I said they've lost a little of the casing flavor, but they're still a good smoke.
I am primarily an aromatic smoker and I have found that it depends on the quality of the actual tobacco. Many aromatics do not contain high quality tobacco and are so encased with PG that aging will do nothing (i.e. Captain Black, Palidan Black Cherry). However, I do feel if you buy premium aromatics I do think it makes a diference. I cellar MB Vanilla Flake, many Peterson Aromatics and Solani Sweet Mystery and I can tell after just a couple of years it makes a differnce. I also do not agree with the thought that the flavoring will dispate over time. If the tobacco is sealed in an airtight container there is no where for it to go. Again, this dpends on the quality of the aromatic.
I also have what you are saying. Where I was going through a lot of different blends and jarred a bunch of them just to preserve them. I have about 30 masons that are like this. If your goal is to see what aging does. Seal it tight as possible, put it somewhere dark and forget about it for a few years. Otherwise, keep them in easy access and open them when you get an itch for it. One thing you can do to see if aging is working...over time, a mason jar with tobacco in it will seal itself due to the oxygen being consumed by the aging process. If you have a jar that has sat for several months that has not vacum sealed itself, there is probably not much going on inside. The opposite of this is, I have had several mason jars, even after removing the outer ring, were difficult to remove the seal.
With all of this YMMV.
When I first started pipe smoking in Dec. 12 I bought two pounds of bulk aro from 4Noggins. I still have most of this order in jars because I rarely smoke aro's now. I hope they improve but I have no idea what to expect when I open them.
I can see where aging an aro might not improve the flavor, in principle. But, you have moisture, sugar, and starches (as long as there aren't too much preservative), I would think that fermentation is possible, but it would have to be a blend that fermentation would benefit the flavor. But, most likely the issue you would have to deal with is mold from handling, especially a few ounces out of a bulk. I jarred up some of the first aros that I "tried out" before finding my blend spectrum. A couple of of the heavier cased sweet aros developed a white film of mold. And, I did try out a couple of cavendish blends recently to find that the flavors had diminished leaving behind just a nasty tasteless burly. It also had a bite that it didn't originally have. It had aged, but the aging didn't make it necessarily better.
Just like most, I hate to throw out a perfectly good tobacco. I have given away a few to friends looking to try out the pipe, but I just can't bring myself to throw them away. So, I will keep my jars till I have the urge to try out one of the non-moldy aros later, or maybe play with them by adding some other condiments to them.
I agree that it will taste basically the same years later. I have several pounds of aros in my cellar, though most are not very old. I do have some cavendish blends that I've had jarred for 4 years or so in my rotation, they smoke almost exactly the same as when they were new. English/Balkan blends and Va based blends are the ones that will benefit from aging. I have some 7 year old Mac Baren "Roll Cake" that is very good, as well as some FMOTT that has some years on it that is awesome! Don't worry too much about the flavor of your aros changing over time, but as far as them keeping, they should be fine.
I agree with eaglerico it all depends on the brand. I have Carter Hall that has sat for about 10 years. One of those 14 oz tubs you can buy for like 20 bucks. While I personally feel the tobacco has mellowed and is a better smoke now than when I bought it, it really hasn't "aged" all that much. Now the counterpoint to that would be my Mac Barren Black Ambrosia I won't even consider smoking for at least 7 years from purchase. Because the MB Ambrosia is a better quality tobacco it does benefit from the aging process. I age my tobacco by simply never opening the tin until I'm ready to hydrate the tobacco and smoke it. MB Ambrosia out of the tin is bone dry and for me is a awful smoke when dry as sawdust.
I smoke a lot of aros and I don't let them age. I do let them breathe for a good 4hr or so in an open mason jar then close it and let it rest for a week or so. If it needs drying I do it a pouch at a time for what I'm going to smoke that week.