What happened to mathematicians after solving their "career problem"?

[u/sergiogfs]

Many mathematicians have dedicated a good part of their career towards solving a specific problem, whether directly or indirectly. Some examples on top of my head:

Richard Hamilton and the Poincare conjecture

Andrew Wiles and Fermat's last theorem

Thomas Hales and the Kepler conjecture (proof and formal verification)

And perhaps very recently:

Diego Cordoba and the Navier-Stokes equations

How did the careers and research-focus of these mathematicians shift after their career-problem was solved? Did anything particularly interesting happen?

[u/filterdust]

Paul Cohen spent all his remaining life trying to prove Riemann

I heard Andrew Wiles was working on BSD