The three batteries I've bought based on what I can discern from the codes on the battery, appear to be about 2 year old NOS. Yuneec says they're good to use, I get about 13 minutes flight time on days below 40F when I hit 14.7 or so, I tend to land with juice in the box out of an abundance of caution right now. And that would be 13 minutes of active flight, record the whole time, typically half the controller set at "half rabbit".
I think however I'll go with a brand like GiFi in the future, my main concern is the quality of construction first and foremost, second is quality of cells. And honestly you have to be careful because there are chinese factories actually "counterfitting" cheaper brands that are popular, and it makes sense, unless China goes after it's own companies, whose gonna say anything>
Turned one into Amazon, they removed the lisiting and all it's associated feedback, gave it a new ASIN and relisted it as a new item with no feedback.