Seeing as how MMOs attempt to convey the journey of life and accumulation of knowledge and experience through leveling, it isn't hard to imagine a game in which your characters age as you progress. In strategy games like The Sims and some RPGs like Fable, aging is built in to the system, adding a layer of immersion as you see your characters grow older as time goes by. When you contrast this with the stuck-in-amber preservation of MMO characters, forever beautiful and flawless, a possible missed opportunity beckons.
When developing Warhammer Online, Mythic got players excited about a "character growth system" where your avatar would gain size, facial hair and scars with age. While this got the axe, it also got players thinking and talking about the subject. So should characters age in MMOs? Would the immersion be worth the difficulty and debate over how such a system would function?