The most major changes occur over the first six months to a year, though there is significant improvement in two months. After a year, it takes about another year to notice much difference, then about two more...see a pattern? After about 10 years, things really slow down. But, smoking tobaccos that have been aged 2-5 years is a real treat, and worth the wait, for some blends. GL Pease, 1998-03-08
There is really no optimal interval, but there are ranges that are significant. The first real difference is noticed after a couple months in the tin. Here, the melding of the flavours has really started to take place, and there's a little more "evenness" throughout the smoke. After about 6-months or so, significant fermentation has begun, and the flavours really start to become enhanced. Beyond that, 1-year, 2-years, 5-years show distinct changes, though not as dramatic as the early ones. Aging continues, but at a slower pace. There's not a lot of difference between a 5-years old tobacco and one which has been aged for 6-years, but at 10-years, it's noticeable, though subtle. GL Pease, 1999-06-01
As with wine, the best thing to do is to buy plenty, cellar it carefully, and taste it often - at six months, at a year, at two years, again at five. It is better to enjoy it sooner, and dream of what it may become, than to find it over the hill later, and lament what it might have been. GL Pease, 2000-05-03
It seems that somewhere between 12 and 24 months is something of a magic number, and that seems to be pretty universal amongst most tobaccos I've experimented with. GL Pease, 2002-05-20
While six months makes quite a difference, I've noticed that 18 months to two years is really where the turning point lies. You can expect increased complexity, a rounding out of the flavours, enhanced sweetness, and greater depth. GL Pease, 2004-08-05