It varies greatly from tin to tin.
The circular European tins are among my favourites; the American "cans" are also fairly good.
The rectangular Gawith-style tins are a little risky; the Penzance-style tins even moreso.
Dan Tobaccos are ALWAYS too dry in my experience, straight from the tin...
Large Solani tins aren't sealed whatsoever...
Then of course you must take into consideration that ANY tin could've been dinged enough in transit to render it useless for aging; that's why you must inspect them all upon arrival.
If in doubt about the tin's integrity, then throw the tobacco in a mason jar.
I tend to avoid that for the most part, however, because I think something is lost when you open the original tin without a pressing reason... You stop the aging process and it may take years to resume again, or it may never again produce the same microflora that you started out with...
In general, keep it in a dark and dry and cool to room temperature location. Consistency of temperature is key; you want to avoid any extremes or big fluctuations.
Original tins are ideal if they aren't damaged or unsealed or prone to failure. (This is your judgment call)
Virginia tobacco will supposedly improve for decades when dealing with quality blends. These are rich in sugars and will benefit the most from aging.
Burley tobacco supposedly doesn't change very dramatically, becoming perhaps a bit more mellow and refined.
Oriental tobacco probably improves to some extent, though I am not familiar with what aging does to that type.
Latakia softens and marries within a year, and will continue to get milder. It may or may not be over the hill in 5-10 years, depending upon the composition of the blend and the smoker's tastes. (Some like ancient lat blends)
Perique tobacco softens and its spiciness fades, for I have seen a dramatic difference in as little as one year in some cases. This is another time when your mileage may vary. It will, however, remain good for many years.
And, finally, aromatics. I personally think that these are not worth cellaring because if you like them for the topping/casing then that is the first thing to go. Exceptions may be made for some blends with quality bases of Virginia or Burley that would probably benefit from allowing the tobacco to shine through. Some of the drugstore aros could also probably use some time to evaporate some of their excessively artificial flavours, but you may/may not like what you are left with...