I have 'mixed' for over 50 years, obviously before e-liquid [as we know it] even existed. When I measured viscosity, from beginning to end [start to finish], much of it in racing oils before synthetics, and then afterwards, making blends would 'tell' on themselves, meaning which blended better, faster,,stabilized better, etc. depending on when the heat was introduced, and how and what rate it was introduced. For my use, when I began with e-juice, I followed the pattern that I was accustomed to.
We [vaping world] have many methods, and a consensus of what works with excellent results[individually]. My approach has been from my own experience, and the difference in my method may create a slightly different juice than others, even using the exact same recipe. The jury is still out because we haven't had a long term study to even begin to understand what is THE way, yet in the interim, we have created some awesome flavors.
Given the ingredients, and the methods, I still believe that mixing e-liquids benefit most from a room temperature mix of ingredients, and the only heat that needs to be applied is from friction DURING stirring, especially when using liquid nicotine. I am no lab scientist, just an old engineer with lab experience, and realize there is more than one way to achieve a desired outcome. I also cook and bake, from scratch, every day, and use the same philosophy.
All being said, there is another side of the equation, and that is in the use of simple equipment.......and from that alone, the results can be far apart. It can be as simple as one who shakes his batch with little head room in the bottle versus one that leaves the bottle only 3/4 full. Or the size stir bar [and shape] versus the size [and shape] of the vessel used to stir in when using a magnetic system......versus one using a sonic approach.....or a crock pot, frother, mini paint stirrer, etc. The exact result from the same recipe will and can only be different in some way, and although not necessarily bad or wrong, but not exactly the same. [if any of this makes sense]
I am curious why you have a shortened shelf life of shake-n-vape [or ready-vape]. I understand some are great at first, then after aging, they change, especially custards, but some are great almost immediately then just get better......for example, Alisa's Bust-A-Nut.......but there are many more. Just curious why you mentioned that [the down side of "ready-vape" e-liquid is the shortened shelf-life, ]
Anyway.....ramble as I fkn do, I hope I have made some sense and it doesn't seem like jibberish.