Acceleration and deacceleration already not what it used to be. Streight line sprints are still there, so his off the ball movement is gonna be good for couple of years to come. Accelerate with ball in your feet and without it, two diffrent things.
Bottom line, hard work/training checked, wear and tear does not show any sign of that, genetics not sure is he genetic freak, but good genes are there. I have good feeling he is not going to slow down any time soon. What we see now, not CR from Man.Utd days, we are gonna see it atleast 3-4 years from now.