Wales international Giggs, who has made more than 950 appearances for United, turned 40 last week.
But his performance in United's 5-0 Champions League victory against Bayer Leverkusen four days ago underlined how much he still has to offer.
"He always says he will play as long as he is contributing, and there is no evidence of his contribution waning at the moment," Scholes told BBC 5 Live's Sportsweek programme.
"I am sure he can play until he is 41, 42, maybe even 43. As long as he wants to, he will be able to play.
"The way he plays, he sits in midfield, he controls a game, he can make a pass, he can defend, he can still run up and down all day if he wants to. I really think he is capable of doing that."
Scholes paid tribute to Giggs' fitness regime as being crucial to his longevity.
"He is an incredible player, really," Scholes added.
"To still be doing what he's doing at is age is no surprise when you know the man, how well he has looked after himself over the years.
"To play football these days you have to look after yourself incredibly well.
"It is such a professional game these days, the players are so fit, but he is a natural athlete.
"He will do all his yoga, he will eat the right foods, he prepares himself meticulously for what is needed as a Premier League footballer.
"Everything he does is geared towards his fitness and keeping healthy.
"He's managed to do that. I watched him the other day and he was by far and away the best player on the pitch.
"To be doing that at his age is a special achievement.
"As a United fan, I hope that can continue because we know that with a Ryan Giggs in the team the way he played the other night we are going to win more games than we are going to lose."