It is not surprising that pipe tobacco takes an inordinate time to age, since the tins are hermetically sealed, unlike cigars; this is a thing that has come up in the wine industry lately too, since New World wineries are increasingly jumping on the bandwagon and bottling ever more serious wines with screw caps/artificial cork. It's a little early to make sweeping statements, but things certainly happen differently - something like a loss of character, more than aging as we recognize.
There's sufficient air in the tobacco tins and between the leaves to facilitate aging, and after all, slow aging is good aging. Very few people do it, in the case of pipe tobacco at any rate, so you'll be in a fairly unique position. The results can be remarkable; a few years back I was demolishing an old wooden barn on my parent's land, and an old jar appeared in the wreckage, which turned out to be Alfred Dunhill "My Mixture"; from the state of what was left of the label it had been somewhere cool and dark, and as far as I was able to ascertain, it was produced between 1907 and 1910. Upon opening it I was astonished to find that it possessed still a natural moistness, and its bouquet was like nothing I've ever encountered in tobacco; really rich dark chocolate, nutmeg, coffee, molasses, spices, dried fruits and leather were dominant, but there were dozens of other facets to this aroma - so complex. To smoke it was phenomenally smooth, and once more, if I had to seek adjectives to describe the palate it would be to venerable Cognac, Calvados, spice and mocha that I would look - really remarkable. Once opened the palate began to coarsen and dry up very quickly for some reason, so I had to smoke it over a period of about a week (woe). I really look forward to my own, intentionally aged cigars/tobaccos reaching such points of mellow complexity, but it will be a long while yet; you are to be congratulated upon your foresight.
Aging cigars changes the playing field entirely, and I couldn't agree with you more about their subtle complexities. There's a bar I frequent in London - The Lanesborough Library Bar - where they have a humidor stocked with aged cigars, some pre-war, in perfect condition. Since, unlike yourself, I had not the foresight (and age) to cellar cigars/tobacco until recently, it has been fortunate that I've been able to sample such delights there for myself; I have also begun "cellaring" cigars and tobaccos - I prefer Cohiba Robusto and Esplendido, although there are many others that offer complex, delicious flavor profiles - along with wine, although I have not been doing so for long enough to fully relish the blossoming complexities. It is nice to see how they evolve over time, although I must add that aging tobacco is a more demanding pursuit than aging wine; it's not as if one can just lay them down and forget about them for 20 years, is it? Perish the thought that you forget to add water for a time, or be somehow prevented from doing so! Oh, one other thing that I wanted to mention is that the above bar has an Armagnac/Cognac list going back some 300 years, which they entitle "The Liquid History"; should one order, say, an 1812 Cognac, Napoleon's retreat from Moscow and other significant events of that year are described, which I find stimulating when drinking that year's produce. Conversely, should one wish to commemorate the battle of Trafalgar, say, one can enjoy an 1805 Armagnac there. I find that such mellow, mouthfilling yet soft, intensely complex yet graceful, exquisite brandies accompany such venerable cigars/tobaccos beautifully. Naturally, these pleasures are not cheap, but many sublime things are not.