Also chewbacca didn't seem to age. Wonder what his secret is.
Wookies have a lifespan of several hundred years. While the 30 year span from ROTJ to TFA for humans might be significant, in the lifespan of a Wookie, 30 years could be more like 4-5 years for us, possibly even less.
So his secret is good genes. Good Wookie genes.