When I initially asked this question I was vaping a lot of Backwoods Brew. I don't know what makes Backwoods Brew so different from just about every other juice, but I always found that 2-3 weeks made for drastic improvements. Halo I find 7 days does the trick. Just about every other juice I've had around is fine out of the mail and doesn't go through any significant changes, my own juice included.
So I would still answer YES today, but I find that 98% of the time the answer is NO. If anything, age hurts juice more than it helps it. The chemical changes brought by the passing of time with tobacco and spirits make magic, but unfortunately for the most part the chemical changes that occur in our product fall under the heading of Undesirable Degradation. IMHO.
I suppose that is because with tobacco, aging in a controlled environment allows for fermentation of the natural sugars in tobacco. Tobaccos with high sugar contents continue to improve literally for decades in a controlled atmosphere. Virginias, and to a lesser extent Orientals. Burley doesn't contain as much sugar and doesn't benefit much from aging, and Latakia actually loses its edge with time. Similarly, good spirits probably experience a little of the same, coupled with a desirable mellowing that occurs as degradation sets in.
With our product, the degradation isn't so desirable. I am going to go along with the accepted knowledge on this subject and say that juice should be vaped within a year of purchase. Any longer than that and chemical decomposition is going to do undesirable things to the flavorings and nicotine. IMHO.