So how long was Hurt the Doctor? Because Matt Smith didn't age a day in 300 years; Time Lords clearly age incredibly slowly. But John Hurt goes from youngish to elderly. He must have been around for a long, long time.
Subjective time, at least. He is in the middle of a Time War, after all. By the mini-episode, it apparently threatened not just to be destructive, not just to kill everyone, but to actually destroy the Universe. Who knows how many loops he lived how many times over, how many knots in the time-space continuum he had to traverse?