Magus cultivation is not something achieved in a single day.
After recovering his internal energy at the inn, Aizen had no intention of continuing his meditation.
The practice of the Absorption Technique involves using one's internal energy in conjunction with a fusion method to refine and assimilate foreign internal energy into the body.
Although meditating to cultivate internal energy can be beneficial, especially for refining foreign internal energy as one's internal energy grows stronger, it is ultimately not the optimal way to train the Absorption Technique.
This fourth-tier inner cultivation technique is not particularly precious to the Heavenly Demon Clan.
Most entry-level disciples, and even some of the top inner sect members, have likely learned similar techniques of this tier.
Apart from the supreme Heavenly Demon Sutra, the Heavenly Demon Clan has an extensive collection of powerful techniques.