For the past year, Cristiano Ronaldo said repeatedly he’ll eventually retire at Real Madrid.

On Monday, he’ll act on that promise.

The Portuguese superstar has agreed on a three-year contract extension with Los Blancos until 2021, when he will be 36. He has mentioned that he could play until he’s 40, but his role will no doubt shrink as the years pass.

Keeping Ronaldo is a no-brainer on the surface. He’s synonymous with Madrid, and he’s still its standard bearer. Though his recent performances don’t inspire much confidence – he failed to produce a shot on target in Sunday’s win over Leganes – there’s no doubt he’s still got a seventh consecutive 30-goal season in him.

It’s his longevity that raises questions. At 31 years old, Ronaldo’s still capable of playing at a high tempo, demanding the ball in every situation, taking on defenders, and sprinting into space.

He just can’t keep it up forever.

If both the player and club truly intend to see out the new deal – lest we forget contracts in European football serve to protect a player’s transfer value, and nothing more – then there has to be a long-term plan in place to make use of the latter years of his career.

Last week seemed to signal a changing of the guard, as Gareth Bale recommitted his future to Madrid until 2022, on a contract that’s reportedly banking him £350,000 a week. No other player is making that kind of money, not least Ronaldo, although it remains to be seen whether he’s going to earn a pay raise himself.

Money itself isn’t an issue for Madrid, but the wage structure sets a precedence. If Bale’s making more than Ronaldo, that’s a clear shift in the Galacticos’ paradigm.

But even he must understand his limitations. By the time he’s 36, Ronaldo will no longer have the physical characteristics to play as a roaming winger.

His athleticism is the biggest reason why he’s been able to dominate matches. Former Madrid assistant Paul Clement once recalled early mornings when Ronaldo would stay up for an ice bath, and other times when he called in the physio for a 6 a.m. session.

These are the tricks. He also has an incredible diet and commitment to fitness.

But as time goes on, there’s every chance he will assume a more traditional No. 9 position, which would save him from the intensity of covering in excess of 10 kilometres a match. His game is all about twists and turns, and keeping the opposition guessing, but he admitted last year that a transformation is taking place.

“I’m different now, I’m more a penalty-box player, not so much on the wing, because you score more goals from there, so I changed my position slightly,” he said. “It’s been a natural change and it’s certainly kept me happy.”

In 2015-16, he had more shots in the penalty area (130) than any of his previous La Liga campaigns, and his dribbling statistics are on the decline. He’s already taking a more direct route to goal.

Much is made of his individual nature, the lack of team support, and the times he protests a teammate’s decision to shoot instead of pass to him.

The way he plays in itself is selfless: He tracks back to collect the ball and initiate plays. Ronaldo as a pure poacher is not the Ronaldo that became one of world football’s greatest-ever players.

Madrid may well do better to go younger. If Alvaro Morata is there, he’s a much more logical option as a striker. Morata has the same mobile traits as Ronaldo, and he’s a product of the Santiago Bernabeu outfit. His future is the club’s.

It makes the idea of a three-year extension all the more questionable. Couple Ronaldo’s age with Madrid’s ruthlessness towards club icons, and the conclusion isn’t so easy to ascertain.

President Florentino Perez ushered out Raul and Iker Casillas – who accrued far more than 1,000 appearances together in the famous white shirt – under unceremonious circumstances.

What’s to say the same won’t happen to Ronaldo?