Seoraj gives him a sidelong look, half-wry, because he can in fact pick out what that's about. "You spend your life in battle, you'll feel old, too," he says, mildly, and...in fairness, nothing about his interaction with Bruce thus far indicates that he wouldn't perfectly understand the sentiment. The awareness of that is there in his tone, too, amused but accepting that they're all in on the joke, here. (The horrible joke, but you deal with your life however you can, and this is one way Seoraj uses.)