I’d say older than 3yrs. And sheng as opposed to Shu (ripe). The former is pressed and left to age, and the latter is cooked, speeding up the fermentation process, thus mimicking aging.
The two have completely different characteristics and taste differently. I’d say Shu is more forgiving in terms of steeping, but on the other hand is a lot heavier in taste, with more umami (fishy flavor)
There is a term used mainly for Pu-Erh teas - being tea drunk. That describes literal caffeine high invoked by ingesting a lot of caffeine relatively quickly.
Speaking from experience - the worst that had happened for me was not being able to sleep the night after drinking a lot of strong gong-fu brewed Pu-Erh teas.