Freshly made
juice benefits from being "steeped" for a few days (or longer). It allows time for the flavorings to distribute themselves through the
juice, and can turn some flavors that initially tasted gnarly into delicious juices.
Everyone has their own personal preference on how they like to steep, personally when I get
juice, I'll try it out and determine if it actually NEEDS steeping. Many juices don't. If it does need steeping, I'll take the cap off and let it sit for about 7-12 hours, just to get any perfumey/residual odors out of the bottle. Then I'll shake the bottle thoroughly and re-cap it. Shake the bottle every day, or every other day or so, and open it for a little while to bring in some fresh air.
I've found a lot of chocolatey juices will get WAY darker over time, as well as any juice with higher concentrations of nicotine in it (nicotine turns darker as it's exposed to oxygen, I believe?)
Some people have taken to brute-force steeping, putting their bottles of juice in agitator machines to rapidly steep them. It's really up to your personal preference how far you wanna take it. Some juices I've tried actually get too sweet after being steeped, while others lose some of their sweetness and become more tolerable with time.