Unless he dopes to his eyeballs like Horndog it's a bit of a reach to presume he'll be fine at age 35. Especially coming off an injury, with teammates like GT and Bernal nipping at heels. The list is long of guys that age or younger who haven't been able to-- Lance, Contador, Nibali and even the aforementioned Valverde. He won the Giro on a hail mary last year and TD was stronger at the Tour. Could have been a one-off trying to manage the double but he never looked like the world beater he has been.

Like you said, he has managed fatigue better than anyone but that doesn't mean time won't catch up.