NT mixes their
juice in large batches. The site will tell you when the batch was mixed and the recommended steep time. Kent and Katy will not (usually) release a batch before it is steeped to their liking.
Most of their juices however will continue to get better and better with a deep steep, particularly their custard based, bakery and (from what I understand) tobacco based juices.
All the juices I have ordered from them have been great right out of the box but continue to get better with time.
If you go to the NT forum and look for the "hit it or quit it threads" you can get great feedback from NT customers their experiences with NT flavors as they steep and develop as well as how they react with different devices and at different wattages.
Hope that helps.