"He was reliving the battle in Karazhan, and experiencing again that horrible wrenching sensation as Medivh drew from him his magic and his youth. The magic had returned—indeed, in many ways it was far stronger now than before—but his youth was gone, torn from him long before its time. He was an old man now, at least in appearance. He still felt hale and hearty, and had as much endurance and strength and agility as ever, but his face was lined, his eyes deep-set, and his hair and fledgling beard a stark white. Though only nineteen, Khadgar knew he looked three times that and more."
He probably won't die of old age anytime soon if his functions are still that of the age he should be.
Also, you are right.
"Not de-aged. Just freshly-shaved.

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