This is what he has now been taking into consideration for quite some time, it is not unknown to Ronaldo that age is after him and he won't be able to play forever. But many of the critics have to admit that he is doing much better than almost anyone else at his age. Ibrahimovic was an exception and there are very few other players who were able to play well, but there has never been a player I think who was still able to perform on that level not only in the Saudi Professional League, but in the national team. He is still scoring against some of the best players in the world and for as long as he is able to do that, he will be part of the national team and also able to play the national team competitions like the upcoming WC.
Age is a player's greatest enemy, as they can't avoid the fact that it continues to age, which affects their performance. However, it's true that, compared to players his age, he's still a player who can still make an impact on the team, even if not as much as when he was younger.
I'm curious about whether he's interested in coaching, as he certainly possesses the leadership qualities a coach should possess. However, considering his passion for football, the possibility of him becoming a coach in the future is quite high.
It depends on where you are at in your career as a player. First they get better and improve their game with increasing age, but then it comes to a point where physical and mental condition suffers from getting older. Mentally could still be handled by someone like Ronaldo as he has a strong ego and he earned it. His physique is still one in a million for his age and he will be able to compete with some of the best strikers. Maybe the time will come when he can't go the 90 minutes at full speed and effort, but imagine you are a coach of a club or a national team and you have Ronaldo sitting on the bench.

He is a player you could anytime bring on for half an hour or longer. He has all qualities for any game no matter what the result is. If you are behind, he is able to take headers after corners, shots from a distance, free kicks, penalties. I think he can go 3 more years at least.