Have you ever wondered how long a shared link will continue to receive attention? Bit.ly has an answer for you. Their recent study showed that, on average, links have a 3 hour half-life.
The Bit.ly Study
Curious as to the duration of their links, Bit.ly started looking at shared stories. They found that links reached their half-life – the point at which half of the clicks they'd ever receive had already happened – ranged wildly. Stories reached this marker in as little as 5 minutes and as much as 11 hours. So they conduced a full-blown study.
The chart above shows the half-life of content for different points of origination. The social sites examined (Twitter and Facebook) were roughly even, with Twitter showing a 2.8 hour half-life and Facebook showing a 3.2 hour half-life. Direct traffic (emails, instant messenger sends, etc.) show a 3.4 hour half-life. The winner, however, is YouTube.
YouTube has a 7.4 hour half-life, meaning that the amount of attention the link gets will linger. That doesn't necessarily mean that the link will be more effective or reach more people, but it does mean that immediate results should be judged less harshly on YouTube than on other social sites.
All in all, link popularity reaches a half-life at the 3 hour mark. However, there's a great amount of variance both between and within given social networks. Bit.ly's conclusion is that "the lifespan of your link is connected more to what content it points to than on where you post it: on the social web it’s all about what you share, not where you share it!"
Does this mean you can comfortably re-post content after just a few hours? Well, the aggravation you could cause to friends and followers need to be taken into account, but the study does indicate that "linked once" does not mean "linked enough." While keeping far, far away from spam, remember that your links will have received the majority of their love just a few hours after they're born.