Not always. It depends if the tea is still able to further ferment. I’ve had some oolongs and hei chas that were also decades old, but they became weaker over time. They still developed a nice, antique aroma but lost other ones on the way there.
That’s also why I didn’t really have a lot hope when I bought it because I thought that 50 years were too much and that it would just taste stale. But damn was I wrong on that. The baozhong is definitely not as strong as the pu-erh, not even close, but for a tea that has been green-killed and is just lightly oxidized, the potency of just the smell really stunned me.
I still don’t understand how aging non-fermenting teas works and why this one is so much stronger than the oolongs I’ve had but I take it! 
