I'm going to be egotistical and quote myself
The only explanation that made sense to me was that the various components needed time to mix together completely. Until the mixture is completely homogeneous you don't have a "final" product. There's no chemical reaction going on, so it's gotta be about waiting for all the molecules to intermingle and get happy together.
Geoff and his elves are not, to my knowledge, using any kind of powered mixing devices. Without mechanical assistance it's going to take quite a while for the flavoring to disperse evenly through the dense base of PG/VG. Until that process is complete you'll have tiny "pockets" of juice with more or less of a given component than another pocket.
Those pockets will be very small, but only a tiny bit hits the atomizer at any given moment. A thorough shaking of a newly arrived bottle will probably result in any 1ml samples having (for all practical measurements) an equal amount of all components, but on a microscopic level you'd probably find clusters of the same thing huddling together.
It takes hours to vape through a ml of juice, most of the estimates I've seen are in the range of 2-6ml per day. What you get on a single hit is a minuscule fraction of that amount, but the flavor you get from it is huge. It follows that you are getting a
really tiny amount of flavor molecules in a single drag. Those minuscule bits are the problem. If your liquid isn't
completely homogeneous you may notice the taste inconsistencies. One hit may have more PG, another could have more flavor "A," the next hit could be heavy on flavor "B" and so forth.
I came up with a way to speed the aging process up by using a powered mixing technique (read the quoted post for details). Because the results of my test were positive I believe that I'm correct about molecule distribution being the source of the aging requirement on some flavors. I think it's all about how quickly they reach an even distribution.
