Probably there's going to be a tipping point, here, when the frustration outweighs the utility of challenging himself. For now Han isn't looking ahead. This is Ben's task but he's just as invested, pushing himself to match his speed. He wonders sometimes what would have happened if their son had taken after him. By now maybe he'd be a crack shot.

Maybe he'd have rebelled and moved to Tatooine to take up moisture farming. Who knows.

The rock goes sailing and Han stops short, breathing heavy but not losing sight of it.