I have experimented using heat to speed up the aging process; and did not particularly care for the results, so I
personally choose not to. What we perceive as taste comes not only from our tongue, but also from smell (aroma); this is why food often doesn't taste very good when we have a stuffy nose. Some of the molecules that, provide these aromatic notes, begin to evaporate at much lower temperatures (some even at room temperature. Once they evaporate; they can no longer aid the flavor. You will often see this referred to as "flavor fade." As a
very general rule (and there are plenty of exceptions), the more aromatic a flavor is, the more susceptible it is
likely to be to fading.
That said, there are plenty of DIYers, that DO use various heating methods, and are satisfied with the results. Experimenting with, and without heat, is going to be the only real way to see whether it is right for you.
Flavor fade not only happens from heat (though heat will accelerate it), but also, naturally over time. Exposure to air (open tops, airspace in bottles), and storage in plastic (verses glass), and time, all contribute to its potential affect.
My answer answer to this; sort of builds on my previous answer. Some DIYers will automatically age everything they make with the cap off (at least for a few hours, to a few days). Others will do so only when they use certain flavor concentrates.
The primary benefit of leaving the cap off (what many DIYers refer to as "breathing"), is to allow ethyl alcohol to evaporate (EA is used as a carrier in
some flavor concentrates). Ethyl alcohol can produce harsh, unpleasant/unwanted, notes in a finished recipe.
The problem with breathing a mix is that it also aids the loss of those certain flavor notes I described, in my answer to your first question. Again, only by experimentation with individual recipes, will you know whether it helps, or hurts, any given recipe.
I do not refrigerate any of my finished e-liquids (but I also don't make 4 liter batches either
); especially during the aging process. We refrigerate to slow, or halt, the aging process.
Any cool, dark place in your home, that is
safely away from children and pets, should be perfectly fine.
As much time as it takes to taste good to you; or until the flavor no longer changes. The only way you will know how long "that" is (for each specific recipe), is by periodically vaping a little bit to taste. Be sure you are writing down your perceptions each time, so you can refer back to your notes, to have a better understanding of this change.
Also, large batches (like your liters)
may take extra time; due to less efficient/thorough mixing, and total volume.
It depends on the person's individual perception (some taste "sweet" much more than others), how sweet they want it, and the type of sweetener used. As
my (again) very general rule; when I am making a recipe, that I think could benefit from sweetening, I will start at 0.5% and only add extra as needed.
You're welcome; I'm happy to help when I can.
I hope, that from this experience, you have learned that one should
never mix large batches
before the recipe is perfected. That means not only is the formula 100%, but that you have worked out aging, storage, and durability too.
