Aziraphale goes to take a sip of his drink, but the sudden change in question causes him to pause. Not necessarily in a negative connotation, but simply unexpected.

He thinks about it, however.

"...I don't think I ever have." Said truthfully. "Well-- perhaps on the possibility of the world never... Almost ending, I suppose."

But they are who they are. What they are. And he finds it difficult to picture otherwise. The elements would all just be too different.

"Have you?"