I think as long as your mental game keeps improving at the rate or faster than your physical decline you can keep improving. Like Candide and Tanner in their late 30's/early 40's, I think their risk management and planning game is way better than when they were wild young bucks, and it shows because they're both still better than they ever were.
Like I specifically think of this Candide clip:
https://www.instagram.com/p/C2pnmuWtFUB/
The more you watch it, the more you realize its just perfectly planned and perfectly suited to Candide's strengths; one of his signature tricks he has on lock, a massive transfer that's relying on his decades of freeride experience to nail the speed and in-run, and relative to the rest of the face his landing zone looks a fair amount safer, he's past most of the cliff bands and there's ample untracked runout. I mean heck even spotting that transfer is a crazy skill in its own.
I also think the other side of that coin is keeping your body in great shape as you age, even if you're only at 80-90% of your peak that's probably still enough IMO, and I think that's easily achievable in your 30's and probably even your 40's and maybe even 50's if you work hard for it