When I use creams and/or custard flavorings in recipes, they used to take about a week to "be their best", IMO. Then I got a little Norpro Deluxe Mini Mixer on eBay (about $7), and after using it...they're great in only 2-3 days.
The only time I personally let a new eliquid sit totally open, is to evaporate off the ethyl alcohol in it before I vape it. It's not good for your lungs. So, after I've either shaken the beegeebees out of it, or used the little mixer with it, to cause bunches of little bubbles...I let it sit totally open until all the bubbles pop and a white ring forms just above the top of the eliquid. The EA is gone then, and I vape it.
I don't know which, if any of my juices contain alcohol. I have tasted a drop of a flavor or two to see. If you get a burning sensation on your tongue, it's probably due to alcohol. I've experienced that with a couple of mine. Usually, they are fruit/candy flavors in my experience.
What the heck is alcohol's role in a juice flavor? Throat hit? Catalyst for flavors that don't blend on their own?