The blond's words made Clarus pause. "What does that mean? Can't imagine living this long?" His words are concerned, probing, rather than defensive. He doesn't take it as a jab at his age, though sometimes Noctis liked to do so. After all, Clarus Amicitia was only what most would consider middle-aged, and in excellent shape. Rather, he thought it might be a nihilistic or worse thought on Prompto's part. Better to catch those things early.