I have a decent stock of aged NC's, I smoke them from time to time and the only constant I've found is stronger tobacco seems to hold up better to aging. The only CT shade or lighter bodied NC's I'm holding onto are special meaning sticks that probably won't ever get smoked (Operation Iraqi Freedom Cuesta Rey's come to mind).
In general I actually like aged Tatuajes, but again the stronger ones hold up better than the medium bodies. Some of the ones that Pete made to be intentionally as strong as possible to shut up the haters (T110, M80, etc) are friggin fantastic right now, but there aren't too many left out there in the world and it's hard to smoke off the last of them for me when I too am very curious how extended aging will effect these
I agree with Chayse, most NC's are made to be smoked on the spot or shortly after purchasing, but that doesn't mean there isn't still some fun flavors out there to discover. I used to have a box of '05 DPG blue's that were 5 years old when I bought them (found them at a store in NH for a DPG event, had Don Pepin sign the box, then I showed him the date on the bottom and he smiled big and said I was going to enjoy them), those things had a sweetness to them that could never be found in a fresh blue.
Also, another note, if you have a chance to try a very well aged Opus X jump on it. I never really bought Opus because I could find plenty of other cheaper stuff I liked more, but then I got the chance to buy some that were 10 years old (15 years now) and it was a whole different beast. I only have a couple left, but it may be time to revisit. The most fantastic sweet mustiness that burned it's way into my memory, not super complex but that flavor was fantastic and I could recognize it anywhere now
Come out to Denver and I'll find some cool stuff for us to burn