I quite like this paper. Does a great job laying out scientific support for things we already "knew" in our guts - like having retirement ages at around 65, for instance, being an ideal milestone to start transitioning folks from leading hard work to supporting activities.
Where I worry is that these papers will be used to justify ageism. Looking through these comments, there's quite a lot of positions being bandied around that I've heard justify some truly atrocious hiring/firing decisions before, and we need to be cognizant of the reality that age alone is not an indicator of success or failure for a given role or task. It's helpful to keep looking into this, but we also need to be aware of our own biases.