User blog comment:Yungbeatz/Do You think Isshin Is Stronger Than Aizen?/@comment-2038785-20100502204020

Well seeing as Isshin has gotten this far without releasinjg his shikai he must have some really special hidden up his sleeve to have survived this long when others were cut down in a blink of an eye.

Also Aizen reaching the limit of his shinigami self could just be the result of becoming one with the hoyuku - which is very yoga if you ask me. lol.