Personally, I think it's the opposite. Players with high IQ (like Stone) who don't rely on speed tend to be more productive into their later years (see: Pavelski, Giroux, Thornton, etc). Everyone loses speed. But the drop off will be much more severe for a guy like Duchene vs. Stone, and Stone thinks the game much better (because he's had to). The transition to being a 32+ year old player who can't rely on physical traits will be much easier for him. If Duchene loses speed, he's lost. If Stone loses speed, he's pretty much exactly the same. Karlsson, I think has both. It'll take a couple of years to adjust (like it did for the Gonchar's and Zubov's), but he'll be able to make that transition.