When does a news story getting boring online: Two hours after posting? Four hours? Wrong.

A new study finds it's actually 36 hours.

An excerpt from the NYT story:

The physicist who led the research, Albert-László Barabási of the University of Notre Dame, said that the paper’s conclusion should give journalists hope, even in the era of instant news. Dr. Barabási said that traditional ideas about the way people use the Internet would have led researchers to expect a much shorter half-life, more like two to four hours.

“You can spin it two ways,” said Dr. Barabási, a specialist on complex networks. “Gee, only 36 hours is the typical half-life of an article. Or gee, I would have expected it to be shorter.”

Editors of online news sites said the results confirmed what they experience day to day.

“It’s remarkable to watch how the readers find their way to what they’re interested in,” said Jennifer Sizemore, managing editor of the news portal MSNBC.com, which is owned by the Microsoft Corporation and the NBC Universal division of the General Electric Company. “Sure, the top news story always gets a ton of traffic. But sometimes that second-to-last headline near the bottom of the page won’t be far behind. And there are features that will draw strongly for a week or more. Even once they’re no longer featured on the front, they are prominent throughout the site.”

Neil F. Budde, general manager of Yahoo News, said his site must balance a variety of competing interests: frequent visitors who get bored by even slightly stale news, less frequent visitors who won’t know what has happened in the last few hours or even days, and the editors’ own news judgment.

“What would be ideal would be to keep track of when you were last on our site and present a package of news that would be different than what others see,” said Mr. Budde.

He said that the site had so much traffic that it was hard to conduct detailed research along the lines of Dr. Barabási’s study. But, he added, “we do have real-time statistics for the headlines that appear on the front page,” and “you can see that click rates go down after a couple of hours.”