@Shadav, if You are talking about leaving the cap off the concentrate itself, then I have to repectfully disagree with Fran on this one. Do NOT breathe concentrates.
Concentrates use ethyl alcohol as a solvent/carrier when one (or more) of the compounds used in the concentrate won't stay in solution in regular PG. If you allow the alcohol to evaporate off (in the concentrate) those compounds can fall out of solution and ruin the concentrate. Once the concentrate is diluted, by incorporating into a recipe; there is enough other carriers. that the alcohol is no longer as critical, and can safely be allowed to evaporate.
So, in other words: breathe your mixes/recipes. But, don't breathe your concentrates.
As for TFA chocolates (in general); I personally don't think they are their best concentrates. I would be inclined to look to other mfgs. (like HS, VTA, and WF) for better options.
If you think it is too much flavor; you could also draw off a little bit of your current mix, and try diluting it with some unflavored base. Just a small amount should give you an idea of whether you are on the right track or not.
I don't know if you have a harbor Freight near you; but they are another good cheap source for DIY tools. I have bought both:
16pc. screwdriver set ($4)
and
32pc. screwdriver set ($7)
and they work great!
Harbor is also a great place to find small pliers, cutters, and the like.
I know you said your sister-in-law worked in Idaho. If the shop happened to be Vapology; I would
LOVE to get their recipe for Iceberg! It was the mild wintergreen (almost lifesaver) e-liquid that finally got (and kept) me off the stinkies.
Trying to replicate it, is what got me started DIYing, though I never got particularly close.

I would be thrilled to have that back in my daily rotation.