The way I used to test if a
juice was steeped enough (before getting into rebuildables and buying juices pre-steeped), I would put a tiny drop on the tip of my finger and taste it. If it tasted peppery or like soap, it wasn't ready yet. If it had a very mild peppery taste but you could taste the base flavors of the juice you bought, then it was usually ready. Make sure you give it a good shaking 1-2 times a day to mix the ingredients together.