Bilbo wasn't young in "The Hobbit"! He was in his late 60's or so, wasn't he? At the time of "Fellowship", Gandalf noted in the movie that he hadn't aged a day since he returned to Hobbiton from the Lonely Mountains all those years before, even though it was now his Eleventy-First birthday! Of course this was the influence of having the One Ring in his possession. Ian Holm could play him perfectly well!
Bilbo was 50 in the Hobbit.
But then I am going by modern standards. Maybe I am not charitable, but something I have noticed about British/Europeans is that they often look much older than they are, as if their childhoods weren't as healthy as they should be and the alcohol has taken its toll. But that could just be me.
sorry for the delay in answer...got called away by three telephone calls and a package delivery and the insect-spray man. *whew!* never rains but pours around here....