William, 33, works about 80 hours a month for his shift with the East Anglian Air Ambulance, which is about two-thirds the amount of hours his fellow pilots that work full time put in, PEOPLE has confirmed.
The royal’s job with the service is his primary role, and he fits in charity commitments and royal engagements around it. His civilian job also enables him and wife Kate to base much of their family life at the 10-bedroom Anmer Hall mansion on Sandringham estate in Norfolk. Prince George also attends preschool nearby.
William has only appeared at two royal events since the beginning of the year, with another one – at the Wales rugby match against France – set for Friday.
With one newspaper columnist calling him work-shy, reports have also highlighted the number of engagements he carried out last year – 122 at home and abroad – which is 128 fewer than his grandfather, Prince Philip, 94.
The charity he flies his helicopters for gave William its support, saying he was a "respected and integral team member." (William donates his salary to charity.)
"Like all our pilots who fly on behalf of EAAA, the Duke of Cambridge is a highly experienced and skilled professional," a spokeswoman says.
"Our pilots work in collaboration with the clinical crew by landing as close to the scene as possible and by expediting a fast and efficient onward journey where necessary by airlifting patients to the most appropriate hospital.
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"Each member of our four person crew takes a full and active role in the work of the charity. The Duke of Cambridge is an active, respected and integral team member."
With his father Prince Charles, 67, not on the throne, William has some time to be considered what is called a full-time royal. And he conceded last year that "no one actually really knows what [full-time royal] means."
He also has the full support of his father and Queen Elizabeth in how he manages his split of work between the private sector and public work.
"There's nothing to say I couldn’t do it for the rest of my life," he said of his work arrangement. "I might be able to and still balance the two. But obviously, at some point, there is probably going to be a lot more pressure and responsibility from the other side of my life. At the moment, I'm juggling the two of them and a young family," he said recently in an interview as he started work at the air ambulance service in July.
Earlier this month, a palace source said that he found the juxtaposition of his royal duties with flying "very rewarding." "He was able to strike a balance between official work and in particular, supporting the Queen, with his job as a pilot," the source said.
A spokeswoman at William's office at Kensington Palace says in a statement, "The Duke is incredibly grateful to have the opportunity to carry out his skilled work with the East Anglian Air Ambulance."
"It is a great opportunity to connect directly with the community and he considers it very rewarding to be part of a team that provides such a valuable, and often life-saving, public service."