Darth Lars said:
The fall of Erebor was supposed to have been a long time ago, but Thorin does not appear to have aged a day since then when he meets Bilbo.
Actually Dwarves are meant to have a lifespan of around 250 years. So it is possible that Thorin wouldn't look much different. In fact he does look like he's aged slightly since the Fall of Erebor.
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