By Patricia Sellers

It’s hard to believe Warren Buffett. A month ago, the guy turned 80 years old. Last week he was in China with his billionaire pals Bill Gates and Charlie Munger. Last Thursday, he flew home to Omaha, slept a little — even though his internal time clock never went out of whack, he says. Since Monday, he’s been with us in Washington at the Fortune Most Powerful Women Summit…sitting in the front row throughout, like the smartest and most eager kid in the class.

That’s how Buffett acts, ever hungry for information and game to share what he knows. Yesterday, the honorary MPWoman (he’s the only guy who comes and stays for the entire confab) took the stage with Fortune Senior Editor-at-Large Carol Loomis and talked about where the world is headed (fine long-term), what to invest in (stocks better than bonds), and what to keep in mind. Here are a few of my favorite Buffett quotes from their session:

“It’s kind of like a church running raffles on the weekend.”
– Buffett on Wall Street, human propensity to gamble ran out of control and derivatives “make a mockery of the margin rules” established after the Crash of ’29.

“What’s the secret of a great marriage? It’s not looks, nor intelligence, nor money — it’s low expectations.”
– Buffett on the relationship between President Obama and the American people, explaining that low poll ratings are inevitable since his Presidential campaign — like most campaigns — ran on “Yes, we can” hopes. “I spend a lot of time at Berkshire setting proper expectations,” he said about managing his own company, Berkshire Hathaway brk.a .

“When you have government and labor and business (working together) with a common urgency, miracles can happen.”
– Buffett on his outlook for China

“I want to throw up.”
– Buffett on the quality of most chairman letters to shareholders. Most are written by the investor relations department, he noted. To write his letter each year, he says he envisions his two sisters and writes to them as if they’ve been out of the loop for a year. “I tell them what I think of the business,” he said. “They don’t want a public relations document.”

“I tap dance to work. I love what I do. The only thing I don’t like is firing people.”
– Buffett on the single downside of leading a business. There’s no retirement policy at Berkshire Hathaway, he notes, and especially at his age, he quipped, “we’re going to keep it that way.”

– “You don’t need huge intelligence in the investment business.”
Buffett on picking great companies to invest in. “If you have a 160 IQ, sell 30 points,” he said.