The initial OP of this thread was for posting recipes and many times other subjects came up such as it is here lately. We have derailed the thread, so to speak. My apologies to the OP.
I've been using the NF flavors that are sold at ECX and HDV for over a year and enjoy most of the flavors in my vapes. Both places indicate that they are alcohol based.. There are a very few flavors that were gross and I won't reorder. I've not had any problems making and mixing my own DIY from using NF. Most PG-based flavors gave me adverse reactions so I switched to alcohol based with no issues.
Alcohol dissipates. It's the carrier for the flavors. When I've bought some from one particular vendor-made organic 100%VG liquids, I've left the caps off for days and the alcohol or perfurmey smell was still there. Caps back on and let them set around for months before I could vape them, so not sure what's up with that. I've tried theirs several times and have now given up on them, so I DIY this type now. I do still, however, buy a couple vendor's 100%VG juices that seem to have tobacco nets in them because I don't want to make my own naturally extracted tobaccos.
There have been some batches of NF flavors that I make and vape the same day with no problems and they are delicious. However, Some flavors seem to need aging before they taste great. We're not supposed to have to leave caps off for more than 12-24 hours, otherwise, if let them off longer, from what I understand, it degrades the nicotine. Some folks don't use nicotine, so that's probably not an issue for them.