#1 Age
Ronaldo is 33 years old and still going strong. He will be 35 when the European Championships kick off. Before then, there will still be plenty of matches that Portugal plays in even if they qualify directly to the finals through the UEFA Nations League.
Given that he is not one to rest at club level, it could all take a toll on him and decide the time is right to step aside from his role with Portugal.
Wayne Rooney was widely tipped to be part of the England squad when he retired in 2017 which was months to the World Cup. Obviously, he will be a key component for Portugal in the next two years at the least but his advanced football age may not allow him to perform at the highest level for his country.
At club level, he has been surrounded by world-class players that facilitated his play but this has not fully been the case at international level. Ultimately, only time will tell if the world will once more get a glimpse of Ronaldo at a major tournament.