Given that Serge is seventeen when the game takes place, Lynx is unlikely to be less than thirty-five. The dialogue portrait used for Wazuki during the Chronopolis flashback looks more like a picture of a thirty-year-old than a twenty-year-old, though, which suggests that Lynx is more likely to be in his mid-forties, possibly even fifty, but probably not much older than that. (That's assuming, as Acacia Sgt says, that he ages normally.)