Realistically as the game continues I would think it likely we will see some aging from them or it will be weird. I mean if we were going into 5.0 and 3 years had past, I'd kind of expect them to be alittle older. Even if they age slower they are at an age where they are growing.

It would be interesting to see if they at any point chose to change the looks of major NPCs. Cid is now sporting a beard he didn't have in 1.0 and I could easily see others changing their looks as time goes by.