The prince of Wales celebrates his 65th birthday Nov. 14. He has been first in line to the throne since his grandfather, King George VI, died in 1952 and has occupied that position longer than any other royal heir.
They say he has spent his life preparing to be king and regards accepting the role as a duty.
Charles has already said he will take the royal name George VII to honor his grandfather.
William IV was 64 years and 10 months old when he succeeded his brother. King Edward VII, Charles' great-great-grandfather, was born heir to the throne and was 59 when his mother, Queen Victoria, died.
The queen is now 87 and appears to be in good health, although she has cut back on international travel. Charles is scheduled to represent her at the meeting of Commonwealth Heads of State in Sri Lanka in November.
If Elizabeth lives as long as her mother, who died at 101 in 2002, Charles could be pushing 80 when he succeeds her.