At the height of Beatlemania, skeptical journalists often asked John, Paul, George and Ringo, “What are you going to do when this is over?”

But for the Beatles, it’s never been over. The band’s legacy is more vibrant than ever, and the business of the Beatles will only be enhanced this year by a burst of activity surrounding the 50th anniversary of their American debut on “The Ed Sullivan Show.” That Feb. 9, 1964, telecast still ranks No. 11 on the list of most-watched non-sports telecasts in TV history, with an astounding 73 million viewers.

CBS will commemorate that landmark with the Feb. 9 concert special “The Night That Changed America: A Grammy Salute to the Beatles.” A boxed-set re-release of their U.S. albums issued last week is kicking off fresh promotion of the band’s music that will run for years and bring new Beatles titles to the marketplace.

More than four decades after they broke up, the Beatles remain the biggest-selling band in history. With domestic album sales of 64.1 million, they are second only to Garth Brooks among the top sellers tracked by Nielsen SoundScan since the music metrics service was formed in 1991. That figure does not include incalculable millions of albums sold in the U.S. from 1964-1990; 20 of their pre-’91 titles have been certified multiplatinum by the RIAA. Their 2000 hits compilation “1” is the fourth best-selling title of the SoundScan era, with nearly 12.3 million sold.

The two surviving Beatles have been no slouches on the concert trail, either. In 2013, Paul McCartney was the No. 12 live draw in North America, according to figures from concert tracker Pollstar; his 17 stadium shows in 13 cities grossed $49.6 million. And while, by comparison, drummer Ringo Starr’s All-Starr Band is a much smaller attraction, playing venues in the 2,000-seat range, in 2012, the last year Starr played a significant number of U.S. dates, his 22 shows grossed $4.2 million (ranking him No. 169 among North American tours).

In addition, the Beatles are among the biggest movers in the classic rock genre when it comes to licensed material — from T-shirts to lamp shades to Christmas ornaments. Cirque du Soleil’s “The Beatles’ ‘Love’ ” has become a Las Vegas mainstay. Homevid releases of the band’s feature films, notably 1964’s “A Hard Day’s Night” and 1965’s “Help,” are perennial sellers.

All told, the band’s staying power defies the gravity of a notoriously fickle business, as Beatles tunes remain a must-have item for music lovers across generations.

The value of the Beatles’ catalog was reflected in the $1.9 billion price paid by Universal Music Group in 2012 for EMI Records’ label holdings, which includes the band’s recordings, originally released stateside by EMI’s U.S. subsidiary Capitol Records. The music is now jointly released by UMG’s Capitol Music Group and the Beatles’ Apple Corps.

Capitol Music Group chairman-CEO Steve Barnett knows first-hand what a rarefied entity the Beatles remain. In the early 1970s, he worked for NEMS, the management company founded by the Beatles’ late manager Brian Epstein.

“At this company, we all feel a tremendous responsibility to advance and protect that legacy. It’s a privilege and an honor that we get to work with this incredible catalog,” Barnett said. “There’s a timeless essence to the music.”

Ironically, Capitol initially had no faith in the commercial potential of the Beatles, even after they had already conquered the U.K. in 1963.

Historian Bruce Spizer, who will present a retrospective on American Beatlemania at downtown Los Angeles’ Grammy Museum on Jan. 28, notes, “Past experience had shown Capitol that British recording artists would not do well in the United States. Add to that (Capitol A&R chief) Dave Dexter’s expertise in rhythm & blues and jazz, and lack of interest in rock ’n’ roll, and you can understand why Capitol did not get excited about releasing Beatles records.”

Nonetheless, a confluence of events in December 1963 led Capitol to rush release of the single “I Want to Hold Your Hand,” which leaped to No. 1 on the American charts. By the time the Beatles stepped on the “Ed Sullivan” stage, they were well on the way to becoming the biggest band in the world.

Capitol-EMI has been minting money off the Beatles’ library ever since with an array of re-issues, live and archival releases. If there’s one thing music execs can count on, it’s the selling power of a Beatles record.

The latest wave began Jan. 21 with the release of “The U.S. Albums,” a 13-CD set comprising the American versions of the Beatles’ albums. Those collections were different in many respects (including different titles, track lineups and in some cases different takes or mixes of songs) from the versions that were released in the U.K.

Capitol Records brass couldn’t have known it at the time, but the changes made to the U.S. releases back in the day were seeding the market for a plethora of re-release options in the future.

“The U.S. Albums” set follows the 2009 release of the U.K. albums in remastered form, which also came out via iTunes in 2010. The platters even returned to vinyl in 2012. The U.K. album box sets, in all their formats, have sold a total of 300,000 units, according to SoundScan.

Capitol separately issued eight of the U.S. albums on CD in 2004 and 2005. The latest boxed set marks an opportunity to re-introduce them to a new demographic, says Bruce Resnikoff, president-CEO of Universal Music Enterprises, UMG’s catalog division. “(There’s) an entire generation who hadn’t seen these particular records the way they were released in the U.S., in one place, in one fashion, with a sound quality that would be satisfying,” Resnikoff notes.

The “U.S. Albums” set also marks the first time that a major Beatles reissue project is being released simultaneously in physical form and via the iTunes store, the Beatles’ exclusive digital distributor. In December, iTunes released “Bootleg Recordings 1963,” a collection of 50 outtakes, BBC studio shots and unreleased demos; the package was likely tied to the extension of copyrights on the 50-year-old material.

“That collection performed very well from our perspective,” Resnikoff says, “and the people associated with Apple Corps and the Beatles felt the same way. I think there’s an opportunity as we cull through the vaults to find additional material like that.”

Resnikoff confirms that a vinyl edition of the Beatles’ mono albums, released on CD in 2009, will be issued later this year on a date to be announced. The 11-CD mono edition has sold 70,000 copies to date. Last year’s “On Air — Live at the BBC Volume 2,” meanwhile, has moved 118,000 units.

This first anniversary wave of titles is just the beginning, Resnikoff notes: “We have a combined global Beatles team in a partnership with Apple Corps and the Beatles to not only discuss what we’re doing now, but to bring forth a global strategy going forward, well beyond six months, 12 months or 18 months.”

Beyond UMG’s exploitation of the Beatles’ work, other projects will likely see the light of day. Rumors continue to circulate that the Criterion Collection, the high-end homevideo company, will re-release “A Hard Day’s Night” this year.

In Las Vegas, the Beatles’ music is the gift that keeps on giving. Cirque du Soleil’s flamboyant production of “Love” at the Mirage has been running for more than seven years, and will continue through at least 2016.

Cirque du Soleil CEO Daniel Lamarre says the production has played before 6 million people and grossed $800 million. (Capitol’s companion album has sold nearly 2.4 million copies.) The age range of the audience reinforces how enduring the band’s music is, even to those born long after they took that last walk down Abbey Road.

“I think the Beatles are going to be relevant forever,” Lamarre says. “The one thing that is surprising to me is how much the music of the Beatles attracts kids, a younger crowd. … There is something about their music that was and is very, very special.”