Board Thread:General Discussion/@comment-4976518-20140808063123/@comment-46798360-20200904125401

With how powerful Aizen is he could be stuck in a state of permanent bankai. When Zaraki first encountered Ichigo he assumed that since he had so much power his zanpaktou was stuck in an unreleased state, granted this wasn't the case, but Ichigo's zanpaktou is stuck in its shikai state. With the 1000 Year Blood War Arc Ichigo, Zaraki, Aizen, Ichibei, and Urahara are all war powers, all also break the conventional mold of the standard shinigami. So i wouldn't be surprised if Aizen was stuck in perpetual bankai.