you just may be out of luck if you hate the idea of "steeping" or "aging" or whatever people want to call it. In my limited experience I've found that with the suppliers that offer "micro batches" of custom blended juices most if not all will require some steeping. You may be able to find a flavor or two that taste OK right out of the mailbox .... but they ALL will improve with age. My suggestion for you is to NOT throw out any juice that you don't like straight from the mailbox, but put it in a drawer to sample at a later date ... you may find that some that starts out as unvapable toxic waste tasting stuff become quite pleasant after a while.
Also my suggestion for your quest to find an all day vape ... give up the quest .... look for a handful of vapes you like and rotate them. You will waste a lot of time (and money) looking for that perfect juice ... find some you like, and casually use any free samples the supplier may offer to "experiment" with other flavors. Eventually a flavor will emerge that you just can't live without.
Yeah, I'm finding out it's pretty hard to have the patience for steeping, but don't have much choice. I've given up on that perfect juice and will be happy when I can find one I don't mind for more than a few hours at a time. It also doesn't help that my taste buds are trying to recover from almost 20 years of smoking and are probably constantly changing. Thanks for the suggestions!