Mama once told me, "Billy, don't feed the stray cat."
It was good advice, and I'm listening mama. She also told me with pride, "You're the only one marching in step!" LOL! 
I think disco180 got it right:

I think disco180 got it right:
I have been lurking in this form for awhile, I used to participate in TFA flavor threads but have since went to FA flavors so I really haven't been confident enough to participate here but I think I will....anyway I just wanted to add myand say something about steeping and flavoring this is 101
Single Flavor Mixes:
When you mix a single flavor and the percentage you mix it at is too low compared to the base you won't taste it until it binds with the base which dominate the mix. This is where needing to steep is necessary.Steeping is the waiting of chemical molecules to bind and the process of binding happens faster with heat (speed steeping). Re-doing your mix and raising the flavor percentage to its optimal level will allow you to shake and vape without the need for steeping. If it taste good or not depends on the flavor itself and the quality and taste of the base (all nic, pg, & vg are not created equal).
Multi Flavor Mixes:
The same premise about binding, but this time your flavors will also bind and create a totally different flavor or taste (for better or worse). You have to use your dominate or top flavor at the highest percentage and all other flavors lower to compliment your top note or dominate flavor. These multi flavored mixes may taste good at the start but once they begin to fully bond it may taste bad.and it doesn't take that long for the bonding to take place a day or so depending on the volume you mixed. a 3mil bottle will fully develop before a 30mil (common sense).this is why the golden rule is mix small batches.
I said all of this to say
Citric Acid This additive changes the bonding receptors of chemicals (or PH levels) at low doses, at high dosages it also adds a sour note to your mix. If you use Citric Acid it will allow your flavors to stay in their own lanes by changing the flavor concentrate molecule receptors. Binding only occurs when 2 like substances (flavor concentrates) come in contact with each other and they fight for dominance.. So the effect of citric acid changes the structure so that the molecules cant combine (inhibitor).. So if you mix apple with cherry you will have an apple cherry e-liquid instead of a apchely (apple-cherry combined) e-liquid and you will taste more apple or more cherry compared to each other depending on their strength in the mix. This additive will also allow you to mix at higher percentages to taste your juice right away without worrying about steeping or molecule binding when mixed at the proper percentage.
So you both are right...
Bill uses Citric Acid and he mixes at high percentages and he doesn't have to worry about steeping all he has to worry about is if he mixed the right percentage for it to taste good when mixed.
Tepid mixes at low percentages and waits on the steeping/combing process for it to mature and bond. But if you have to wait 8 weeks then your flavor percentages are too low or you are making 100ml of tobacco juice at a time.
The only thing about Citric Acid is its safety for use and proper usage percentages in a mix Bill already shared how he uses it (I think).
Now before I get flamed or called a pseudo scientist here's a couple of references:
Enzyme Inhibition
Flavor enzymatic synthesis UAB Barcelona
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