In social media half life is the amount of time it takes for a post to receive half of its total engagements. A post will get most of its engagements right after it is posted, which is why it is vital to figure out the best time to post. As time goes on, a post’s engagements will start to trail off. You will always have the people who are not on the social medias as much as others, and they may log in hours or even days later and catch up on older posts. Despite the stragglers, a post becomes ineffective after a certain amount of time.
Half life of a post depends on the platform you are using.
Let’s start with the fastest moving platforms: Twitter and Instagram. These platforms measure half-life in minutes. Twitter’s half-life is the shortest with a half-life of under 30 minutes with 75% of the engagements happening in 3 hours. Instagram posts last slightly longer with a half-life that is still under an hour.
Facebook is also quite fast moving, but things do stay fresh for a little while longer. The average half-life of a Facebook post is about 90 minutes with 75% of engagements happening in the first 5 hours.
On the other end of the spectrum, we have Pinterest. People who are on this platform tend to stay longer and they tend to be on Pinterest with a goal in mind. For that reason, the half life of a pin on Pinterest is as high as 3.5 months!
Posting to social media is a great way to get your message across, but if you are posting your stuff once, you are missing out on a good portion of your audience. A lot of people are hesitant to repost the same information thinking they are going to annoy their followers. The truth is that with such a short half life, if your followers didn’t see your post in the first couple of hours, the changes are they aren’t going to see it. As we used to say when we caught a television show on a re-run that we didn’t see: it isn’t a re-run if you didn’t see it the first time. The trick is to know when to repost the information.
Reposting depends on the speed of the platform. We mentioned that Twitter is the fastest moving platform. In the case of Twitter, you should be re-tweeting pretty frequently. You could re-tweet a post the same day at least 4 hours after the original tweet. You can also re-tweet the next day, the next week and even the next month. With Facebook, posts do have a longer half life. Facebook posts shouldn’t be reposts as often as on Twitter. For a message you want to ensure gets proper visibility, you could repost in 2 weeks. As you move down the list to Google Plus, Linked In and Pinterest, you start to get to platforms that have much longer times, so you can repost less, generally a month after the original post would be sufficient to maintain the message you are looking to get across.