User blog comment:Ichigosama/Similarities/@comment-5551986-20130730234516/@comment-11051098-20130731082501

I think he means that Aizen appeared to be an ally, actually one of the kindest captains, until he was suddenly revealed to be THE enemy. And not just since the beginning of the series, but since more than a century already.

And if Yhwach was in a state where he was like frozen, for the 999 years he was sealed, so that his actual lifespan would be 9 years awake + an unknown number of years prior to being sealed, he could actually be going towards the end of his lifespan. As a Quincy, he is logically human-based, after all.