If a person is still in good health at the age of 80 or 90, how many years can he live like this?

Personally, I think it is a blessing for a person and his family to live to the age of 80 or 90 and still be healthy. As for how many years he can live, it is hard to predict. People are eighty years old and healthy, but their organs are aging. As long as this aging organ doesn't work, people will die. My colleague's father-in-law turned 98 in February this year. On his first day at work, he said that his father-in-law should be 100 years old. He ate a big bowl of rice and was in good spirits. After three days, his father-in-law was sunbathing on the terrace outside the house, and his face changed. After he got home 1 hour, his father-in-law left. Therefore, healthy people have to leave early without much warning.