At 92, Sumner Redstone is making no moves toward retiring. And that's a worry for the two media giants he controls, Viacom and CBS.
Redstone is chairman of the board of both companies and he and his family own a majority of the shares in the entertainment conglomerate Viacom and CBS, the television giant split off in 2006.
But even as the two companies face challenges from the shift to the digital age, Redstone has not set up a succession plan.
Redstone has been intentionally vague about what happens when he ends his tenure. Observers have said the likely candidates could include his daughter Shari or Viacom chief executive Philippe Dauman.
"I will not discuss succession," he told The Hollywood Reporter in 2014. "You know why? I'm not gonna die. So why should I discuss succession?"
His planning is in sharp contrast with that of his counterpart Rupert Murdoch, 84, at 21st Century Fox and News Corp.
Murdoch has made his son Lachlan co-executive chairman at both groups and placed his other son James at CEO at News Corp.
- Sense of urgency -
A sense of urgency is growing over the future of Viacom and CBS, companies whose health may be nearly as precarious as that of the nonagenarian's.
Shares in CBS have dropped 25 percent from highs and Viacom is down 40 percent. Both face threats from the shift of viewers to Internet-based on-demand services such as Netflix, Amazon and Hulu.
Viacom, which owns the Paramount studios in Hollywood, is seen as vulnerable at its television operations that include the Nickelodeon children's channel and music channel MTV.
Its latest quarterly earnings were disappointing.
Redstone, who is seen little these days outside his Beverly Hills home, has been notably absent from recent shareholder meetings and has skipped analyst calls for the two companies.
He has appeared frail in recent years despite boasts in recent years about his workout routines and antioxidant supplements to keep himself healthy.
Born to a Boston Jewish family in 1923 as Sumner Murray Rothstein, his father changed the name to Redstone in 1940.
After serving as an army codebreaker in World War II and working as a lawyer for several years, he joined his father's company, which managed a chain of cinema houses.
He renamed the group National Amusements and turned it into one of the largest movie house operators in the country, popularizing the "mulitplex" concept.
Redstone was severely burned in a 1979 hotel fire in Boston, but overcame his medical issues, resuming his business and leading a 1987 hostile takeover of Viacom that pushed him into the national spotlight.
In his 2001 autobiography, "A Passion to Win," Redstone recounted the harrowing fire experience in which he had to hang from a third-floor window even as flames burned his arm and hand.
He underwent some 60 hours of operations including skin grafts and was hospitalized several months before being able to walk again.
After the Paramount takeover, Viacom bought the video rental service Blockbuster in 1994 -- one of Redstone's few business missteps -- and in 2000 acquired CBS.
- King of content -
Redstone is credited with coining the phrase "content is king," and that became the mantra not only for Paramount but the rest of the entertainment industry, spurring massive investments in film and television production.
His leadership earned him a star on the Hollywood Walk of Fame.
In 2006, Viacom spun off CBS, separating the faster-growing cinema operations from the more sluggish broadcast assets.
The future of both remains murky without Redstone, but it is seen as likely that one or the other would be sold.
Redstone has been married and divorced twice. He has two children, but has strained relations with his son Brent, who filed a lawsuit in 2006 seeking to cash out his stake in the family business.
His daughter Shari holds a 20 percent stake in National Amusements and would likely play an important role in the company.
She would be one of the trustees of her father's holdings upon his death along with Viacom president Philippe Dauman.
National Amusements remains the private holding company through which Redstone controls CBS and Viacom, giving him effective control of both firms and a personal fortune of some $5.6 billion, according to Forbes magazine.
"I'm proud about the fact that I was born in a tenement without a nickel and now I control two great companies," he told The Hollywood Reporter.
"I'm not arrogant about it, but I do feel pride in having come from nowhere to where I am today."