Idiom or phrase for expressing one's skill/talent has not decayed
Solution 1:
He's still got it.
He hasn't lost his touch.
Solution 2:
He's still at the top of his game.
at the top of (one's) game
At one's best or most skillful.
I can't believe I got the hardest question right. I'm really at the top of my game today!
I think their quarterback is at the top of his game this year—I doubt he'll be able to replicate these stellar stats next season.
From "The Free Dictionary."
Also see here.
Solution 3:
"You haven't lost a step"
Solution 4:
You still got your chops is what I hear.