Just got my first order from MBV! I know i should let them steep awhile but someone told me the Berry and Fruit flavors sometimes be fine to vape right away? Just that they will get better with time.
Some flavors are great straight from the mail - usually fruit flavors. My Blackberry has gotten deeper in flavor, but it still pretty much tastes the way it did the day I got it.
Most flavors, including some fruits, are better with steep time. How much depends on the juice (and your tastebuds). A week was enough for my Cola (which also changed from completely clear to *bright* lime green). Two weeks for Blood Orange (it was vapable before that, but suffered from the "where's the flavor?" issue that some juices have before steeping.) My chocolates and coffees took a month to taste *good*, but they're still evolving and deepening at a month and a half out.
Most mid to light colored juices will be vapeable after a week. At two weeks, they'll be better. At three to four weeks, they'll settle into their "final" flavor.
Generally, the darker the juice, the longer it'll need to steep - coffees, chocolates, most tobaccos, etc. There are exceptions to this. Coconut Cream Pie arrives clear, took a month to get vapeable, and is also still evolving and settling. (The latter is also a very temperamental and not-for-everyone kind of juice... a lot of people get burnt plastic taste from it even after lots of steep time.)
I suggest you try everything out of the mail so you have a baseline. If you have a mini tank, or better, a dripping atomizer, use that, and just try a few drops... you don't want to load up a full tank/carto with most unsteeped juices. Expect them to range from "good, but could be better" to "gross."
Then put them away for a week. Shake them when you think about it. At the end of the week, try them again.
Rinse, repeat.
You don't *have* to do it that way - some people just chuck them all on a shelf (away from light) and wait a month, and that'll accomplish the same end.
But if you're like me and can't afford to buy a closet full of juice, and therefore like to have a *general* idea of how long each juice takes to steep for your liking, testing them week by week is a good way to learn estimates for each juice flavor.