He's reached an age when most of his peers have closed the door on their careers and are enjoying not having to work any more.
But Prince Charles, who turned 70 last week, is yet to take on the role he has been destined for his entire life.
He's in a tricky position – he's itching to become a monarch because there are so many things he wants to achieve. But stepping into the top job will sadly mean he'll have lost his mother, the Queen (92).
While some people may think that waiting for so long to be king has been a waste of many years, it's not as if Charles has been sitting about twiddling his thumbs.
He dedicates his life to royal duties and shows no sign of easing up even though he's entering his eighth decade.
In fact, with the retirement of his father, Prince Philip (97), and with his mother handing over more and more of her responsibilities, he's taken on even more work.
Charles works a seven-day week, usually starting at 9am and often not finishing until after midnight, say palace staff.
He is one of the hardest-working members of the royal family, last year carrying out 546 engagements in the UK and overseas.
Plus, he is believed to have held around 500 meetings behind the scenes on top of those engagements.
A former aide says staff are in awe of how much he does.
"He's phenomenally hard-working," says the former employee, who once got a work-related call from Charles on Christmas Day.
Those who know him say Charles is so diligent with his duties because he cares, he's curious and he wants to make a difference.
His sons admire their dad's determination to get people to do something about issues such as our endangered environment.
"We sit there and speak to him and he gets so frustrated," says Prince Harry (34).
"You can understand why, when he cares that much and he's been banging the drum for this long."
Charles' wife Camilla, Duchess of Cornwall, says he is "driven by this passion inside him to really help – he really wants to save the world."
In a BBC documentary to mark his 70 years, Camilla (71) admits he can be "pretty impatient" sometimes, and Charles himself has owned up to "meddling" in public affairs.
He has been very passionate about causes close to his heart, such as the plight of people living in inner cities and environmental issues, but has also faced much criticism for interfering in matters that shouldn't concern royals.
For example, he has written to and met with UK government ministers about the hazards of plastic pollution.
Several decades ago he was regarded as something of a green crackpot but, in fact, he was ahead of his time and people have since conceded that he was right.
But the prince is still pilloried when it comes to his other beliefs, such as the benefits of complementary medicine.
Charles has said that it would have been "criminally negligent" for him not to use his position to express strong views, even though he is supposed to be apolitical, and to try to help people.
"You are accused of being controversial just because you are trying to draw attention to things that aren't necessarily part of the conventional viewpoint," Charles says.
"My problem is I find there are too many things that need doing or battling on behalf of.
"There are a whole lot of things I have tried to focus on over all these years, [things] that I felt needed attention. Not everybody else did, but maybe now they are beginning to realise that what I was trying to say was not quite as dotty as they thought."
He has also copped flak for having an extravagant lifestyle.
The unauthorised biography Rebel Prince, written by Tom Bower and published this year, added to the unflattering image of Charles as a weak and arrogant person who enjoys the trappings of luxury, is intolerant of those who don't agree with him and supports some bizarre theories.
Charles' supporters say the claims in the book – including one that he travels with his own toilet seat – came from disgruntled former employees.
When asked about the book during a radio interview, the prince said, "Oh, don't believe all that crap."
Those who work closely with him acknowledge that he can be demanding and short-tempered, and that he sets high standards.
With regard to the luxuries, as a member of the royal family, there are times he needs to behave regally. For example, when he entertains, his guests get top-quality food, wine and service.
"He thinks that is right for the Prince of Wales," says the ex-aide.
One thing that has overshadowed Charles' life and earned him harsh criticism is the failure of his first marriage to Princess Diana, and his affair with Camilla.
Mistakes were made, but it's time to move on, says a palace insider.
"He married the wrong person, but that shouldn't define him. There is so much more to him."
Such as being a good father. Much is made of Diana's maternal ability and influence on Princes William and Harry, but Charles too has been a supportive and loving dad.
Sir Eric Anderson (82), one of Charles' former teachers and now a friend, says, "Charles has been an extremely good father. Not everyone can bring up two sons on their own so well."
Charles can also be fun. Simon Lewis, the Queen's one-time communications secretary, says he's enthusiastic and committed with a "wicked sense of humour".
Eric agrees, recalling how as a student at Gordonstoun School in Scotland, Charles was a talented actor who played Macbeth in a school play.
"When the costumes were delivered, the prince tried on Macbeth's crown and said, 'We've got better crowns than this at home.' Everyone fell about laughing. The public don't always see the sense of humour, but I think you must need that to survive."
Simon says humour has helped Charles get this far and when the time comes for him to be king, he will give it his all.
"Charles, the Prince of Wales, is going to be the best prepared monarch probably in history and I think he'll be a good king."