On a generational spaceship, the kind where it's the great-great-whatever grandkids of the people who leave Earth who eventually arrive at the final destination.

Do Clint and Natasha sign up to go and why, or are they selected? Are they people in the middle of the journey, who are born and will die on this ship, and what choices and kind of life do they have? Are they towards the end of the journey where everything is old and falling apart? Or are they nearly at the end, contemplating the landing and how everything is going to change?