Some critics say that Fitzgerald's age (him being in his late twenties at the time he wrote The Great Gatsby) was germane to his treatment of the narrator. Does an "ironic perception" only come with gray hair and wrinkles?
What a great question. This question forces one to contemplate when one comes to really understand what irony is and when one actually comes to possess an ironic perspective.
As for F. Scott Fitzgerald and The Great Gatsby, analytical and critical readers can find both irony and an ironic perspective in the text. Irony lies in Gatsby's uncut books (pages he has yet to cut in order to read). He desires to appear elite and educated, yet a simple turning of a page out of his library would call his bluff--he has never opened any of his books. Irony is easy. Irony is something that teenagers can master (although they typically identify it as sarcasm).
An ironic perspective is typically something a "seasoned" person possesses. One does not necessarily need to possess gray hair and wrinkles, as the question states, to possess an ironic perspective. Instead, one (in the position of Nick) may come to find life so ironic that he (or she) simply becomes jaded by it. The library, Daisy's sophistication, Gatsby's illegal ways, and the affairs of the heart. Seeing so much go wrong, when one wants it to go right, could only bring about an ironic perspective in life. In a sense, why do the characters even try? The answer...to try.