The academy had two sections, one for the youngest generation and one for the youth. The youngest generation started at the age of twenty at the cultivation base of Earth origin and it ended at the age of ninety years. Beyond ninety years you weren't allowed into this section.
The second section started at the age of One hundred years to One thousand years, at the age of One hundred to two hundred you had to be in the divine realm to enter the academy, from these years one would stay as long as you wished in the academy.
Although these years seemed to be many they were few, the aging of the people in this world was slow, being in your thousands was like being in your early twenties. After closing the God realm you were requested to live in the academy, this was beyond what the academy could contain.