Alfred: "But, sir! You're not even in your twenties, quite yet..."
Bruce: "After all my intense training abroad, don't I look twenty-five?"
Alfred: "Well. You do look quite a bit older, sir."
Bruce: "Tell them I'm twenty-five."
Alfred: "Sigh! Very good, sir!"
Several years later:
Alfred: "Sir! Your face! What happened? You look years younger!"
Bruce: "Yes. I fought Ra's Al Ghul. We both fell into a Lazarus Pit before I beat him. Then, upon my return to Gotham, I was kissed by Poison Ivy, just after she'd taken a highly toxic youth-extending potion. Apparently, this is the result."
Alfred: "Whatever shall I tell the press, this time?"
Bruce: "Tell them I got a face lift."
Alfred: "As you wish, sir..."
A few more years later:
Alfred: "Sir! You've become even younger! Why, you don't look much older than Master Dick, and he's been Nightwing for years now!
Bruce: "Another Lazarus Pit bath after a fall into toxic waste, courtesy of Talia. Then, our passion got the better of us."
Alfred: "Gasp! You actually slept with her, sir?"
Bruce: "I'm sure it'll produce nothing negative. You know the drill?"
Alfred: "Like clockwork, sir. Another face lift it is, then..."
A couple more years later:
Alfred: "Yet another rejuvenation. I'd wish for one myself, but..."
Bruce: "Don't. The whole JLA had to die and be resurrected, this time."
Alfred: "I know the routine now, yet another face lift announcement..."
Recently:
Damian: "Alfred, how old was my father when he became the Batman?"
Alfred: "As old or young as he wanted to be, Master Damian."