09-18-2011, 04:18 PM
It isn't that he considered their mortality for the first time, that was never the point; it was that he considered the fact that their mortality was directly challenged by the very faith in him that he instilled. Amy Pond was a very special case among companions - he was there for her as a child, and then led her on for the rest of her life until now. She was built up by that initial experience with the Doctor and for that reason she, and the confrontation of her faith in him, was the perfect thing to bring him to a breaking point in that respect. It was far more than just his companions being with him.