There are no hard and fast rules but a variety of factors to use as guidelines.
Goals: The objectives of a page differ in the life of the page. In the beginning, the goal is to add fans. In order to attract fans, we must have relevant, engaging, and most importantly updated posts. Whether invited to become a fan of our page or if they stumble upon us through another venue (search, another social medium, etc) we must have current info/posts on the site to make them want to be our fan. If there are only 3 or 4 posts that are six months old, the page and the company will be seen as out of date. As a result, fewer consumers will become fans and there would be missed opportunities.
As the page and fan base building starts to mature, the goal continues to be to add new fans but more emphasis is on getting the ones we have to return and engage. So while the goal is a little different, the way to obtain it is the same – relevant, engaging and updated posts. Make the fans want to come back to see what we have posted, participate in a poll, contribute to the conversation, etc.
Changes in Facebook also affect how often to post updates. Recently, Facebook changed the way that posts (whether by an individual or a page) are displayed. Until very recently, the posts were cached and then displayed for 15 or so minutes. Now, the newsfeed is live, in real time. As posts are made, they are displayed. This means that while we have more opportunity for our posts to be seen by more people, we also have less time that they are displayed. So in order to be seen, we must post more often.
Facebook habits by consumers should be considered. Consumers use different media in different ways. Email, we stay logged in most of the time. Radio we listen in our cars or at the office for periods of time (which vary depending on commute). Facebook – we jump on and jump off. We don’t stay plugged in constantly. Heavy users log on daily (but still not constantly) and light users only several times monthly. To be seen, we have to be present when they log on to their Facebook account. The more posts, the more likely that we will have an audience. Unless someone is sitting there with Facebook open all of the time watching it, frequent posts are fine.
Lastly, if someone truly is annoyed by our posts, then they have several options including no longer being a fan, or just changing their own settings so that they don’t see our posts.