Paul McCartney and Ringo Starr are stunned The Beatles still have legions of fans as they initially thought fame would be fleeting.
The legendary group have released what is billed as their final single, Now and Then, on Thursday, utilising past recordings from late members John Lennon and George Harrison.
Paul told The Sunday Times he believed they might last ten years as a group - eerily predicting their 1970 split - but is shocked their music has remained popular for generations.
"When we started," he explained, "we thought that, maybe, we'd have ten years - that was the maximum span for a rock'n'roll group."
Ringo was even more pessimistic, saying that he had made plans to become a hairdresser.
"None of us thought it would last a week!" he added. "Paul was going to write, I was going to open a hairdresser's, George would get a garage. But it went on and then it ended. And at the right time I think. But, you know, that didn't stop us playing with each other."
However, interest in the band hasn't waned - as they've racked up billions of streams even before the release of new music - and Ringo is confident that will continue for decades to come.
"How many streams did we do last year? One billion? Three billion? It blows me away," he continued. "The beat's still going on, you know?"
In addition to Now and Then, expanded versions of their Red and Blue compilation albums are out on Friday.