The future King is understood to have decided to stay in his military role beyond mid 2013, when his current three-year tour of duty as a Search and Rescue pilot in Anglesey ends.
A anonymous senior royal aide told the Daily Telegraph: "The Duke is very keen on his flying, very good at it, and he wants to continue with his military career.
"Should the Duke and Duchess choose to have children within the next few years, he is keen to bring them up as children of a serviceman for as long as possible.
"He is in no hurry to take up a more prominent role within the royal family, and there is absolutely no pressure from the Queen or anywhere within the royal household for him to do so.
"The Duke is conscious of other members of the Royal Family, including his grandfather, who gave up their military careers to take up greater official responsibilities, but he is not keen to do this if he doesn't need to.
"When the time comes, down the line, he wants to be able to look servicemen in the eye and say 'I did my time'."
The extended career in the Forces – William will have already served for six years when his current post comes to an end – is something of a break from recent royal tradition.
William's father Prince Charles served in the RAF and the navy for five years in the Seventies, but left, aged 28 to support the Queen for her Silver Jubilee.
Prince Edward served briefly in the Royal marines as a university cadet, but embarked upon a career in TV production before becoming a full-time working royal in 2002 – helping with the monarch's Golden Jubilee.