"We flew out Saturday night after the show," Donny continued, "then came back Tuesday morning and did a show that night."
How does one learn to survive such a go-go regimen?
"Well, it's what we've been doing all our lives," Donny replied. "She started when she was 3; I was 5. You grow up in that lifestyle, that's what normalcy is."
"You adapt," Marie said. "You learn to bring it when you have to."
The Osmonds said they learned that lesson early on, as the most visible members of a Utah-based family operation that became the white Mormon answer to the Jacksons.
They took their cues from the greats they grew up observing — Elvis Presley, Frank Sinatra, Sammy Davis Jr. — and recognize it now in the likes of Kelly Clarkson and Taylor Swift, singers who "give the audience a piece of themselves," as Donny described them.
"Remember Taylor with the banjo on the  Grammys?" he asked. "She came out and sang her song ['Mean'], and her personality came across. And what happened? Standing ovation."
The siblings were equally admiring of Justin Bieber.
"My little girl, she just turned 10," Marie said, "and for her birthday all she wanted to do was go see him. I sat there at the show and thought, My gosh, this is what all those mothers went through for my brothers in the '70s."
Still, she sounded a note of caution regarding the next generation's use of social media, which she said artists have little choice but to embrace "if you want to be a part of things."
"Sometimes they write a lot about nothing," she said with a laugh. "You can tell a lot about someone's age by what they say or write. I think it's important to maintain some privacy, but that's something you learn over time."
"Oh, I don't know," added Donny, a prolific Twitter user whose online missives often carry a whiff of celebrity roulette. ("Hanging with #MikeTyson after #Barbra show last night in #LasVegas," he wrote in early November.) "I wish I would have had Twitter back in the 'Puppy Love' days."
The former teen idol's eyes sparkled as he pondered the thought. But the Osmonds' plane was waiting; the prospect, however tantalizing, would have to wait.
'A Donny & Marie Christmas in Los Angeles'
When: Through Dec. 23
Where: Pantages Theatre, 6233 Hollywood Blvd.
Price: $25-$150 plus fees