A renowned advisor on U.S./U.K. relations is speaking out this week to warn Meghan Markle and Prince Harry that the may need to “reinvent” their brand to stay relevant in America, as audiences here may not have an “appetite” for them longterm.

Lee Cohen told The Express that while he does not see Meghan and Harry fading away anytime soon because of how desperate they are for the spotlight, he also think they will need to “reinvent” their brand overtime in order to have long-lasting relevancy.

“I certainly think it’s their ambition to remain in the limelight as long as possible,” Cohen said. “And we have a lot of celebrities here, Madonna springs to mind, who seemed to reinvent themselves and remain popular.”

“Considering all of the resources that the Sussexes have at their disposal and considering the extra special qualities that they have, [Like] Harry’s royal status, also shared by Meghan,” he continued. “At this moment, I don’t think in the foreseeable future they’re going to go away.”

“The question is, how long would the public have an appetite to continue to listen to their grievances,” Cohen warned. “Their grievances against the royal system, against the institution of monarchy, grievances against their own family members. And how long will the public continue to be interested in someone’s very private struggles with mental health?”

Cohen also said that he doesn’t think Americans care about Harry and Meghan’s royal titles anymore.

“[America] already recognizes Meghan as the American princess and she always will be, notwithstanding if her title is taken away,” he explained. “Even if those titles are someday removed, in America, they don’t hold any official status anyway. Their only value is promotional and, deserved or not, that has already been achieved.”

Meghan and Harry moved to the United States last year after stepping down as senior royals, and they have since settled in the ritzy area of Montecito, California. There, they have signed lucrative multi-million dollar deals to create content for Netflix and Spotify.

Harry has also been hired by the mental health coaching company BetterUp as a chief impact officer, expected to earn him many more millions of dollars.