This guy ran a 2:43 marathon at age 30, declined after that, and with the help of coaches and gear ran 2:39 at age 42.
He has a companion piece with gear: https://www.wired.com/gallery/helpful-gear-for-marathon-runners/
For me, the takeaways of cross training and stretching help validate what I've been doing. I need to get back to doing speed workouts, but my Tuesday run club is a good threshold run. The pressure of sticking with fast runners keeps me moving.