37 years happened. This is what age does to people. Even Harrison Ford doesn't look the way he looked in Star Wars, for sure. :-/
I was definitely surprised to hear they're using the original cast. They can do a lot with makeup and post, but they can't make the cast appear youthful, short of going full CGI like they did for Jeff Bridges in Tron Legacy. Unless they go to that extreme, the story has to be set decades after the original trilogy.