• by Steve McClellan  @mp_mcclellan, June 28, 2012

A new study from Omnicom’s OMD concludes that the average content posting by an advertiser on a Facebook page has a surprisingly low shelf life: about 18 hours.

Shelf life is defined as the length of time that users provide feedback after content is posted, and for Facebook it appears to be far less time than other media platforms, said Colin Sutton, U.S. director of OMD Word, who runs the agency’s social media practice and oversaw the study.

For example, Sutton says videos on YouTube often have a shelf life that lasts weeks, even months, as word of the content spreads virally.

"That was the biggest surprise," said Sutton, referring to the short feedback cycle for most marketer content posted on Facebook and analyzed by the study. It analyzed nearly 300 content posts across the pages of 10 TV networks over a four-month period, November 2011 through February of this year.

The networks included Showtime and HBO, among others. While the study focused on one category, Sutton said "the general findings still hold" across various marketer verticals. Research found that the biggest impact on shelf life is the actual messaging and content that is posted. Video posts appear to prolong shelf life by 16% above the average, per the study, while photos tend to prolong it by about 9%.

One post a day was optimal -- any less and there's a risk that brand awareness and engagement by consumers will wane, while multiple daily posts are more than the typical fan wants or can keep up with. "The impetus is on content managers to update their pages while not overwhelming fans," the report states.

For marketers that can't or won't post new content daily, Thursdays and Fridays were best for engaging Facebook users, while Sundays and Tuesdays were the worst days. Sutton noted that those findings conflict with a study Buddy Media conducted that found the weekends to be the best time to engage Facebook users.

“We’re not sure if that's a shift in consumer behavior or specific to the category we analyzed,” said Sutton. "We need to do more work on that."

Another striking finding, per Sutton, was that there seemed to be no correlation between the popularity of a TV program off-line and fan engagement online. “That’s a great opportunity” for lower-rated on-air shows to boost their on-line profiles and potentially their on-air audience levels, said Sutton. And the flipside is that popular shows, like Showtime’s "Dexter," can’t "rest on their laurels," because ratings alone won't drive their popularity on Facebook pages.