D: What? Everyone trying to live forever? No. Death is the price we pay for progress, you know.
M: You speak in riddles, Doctor. The Time Lords were glad enough of the Elixir.
D: […] We don't take it regularly like you, otherwise we'd fall into the same trap.
M: And what trap are we in?
D: #Immortality. […]How many centuries have passed while you have remained unchanged. How long since anything here changed?
M: Nothing here ever changes.
D: Exactly my point. No progress.