While there is no universal answer to how often you should post fresh content, there are two key things to consider: consistency and value.
For example: if you only update your blog once a month, but your customers know that by a certain date there will be new content, they will check in around that date.
While more updates may seem like the best way to go, the most important thing to consider is the value your post will bring to your audience. Unless you are a cook, a picture of your lunch everyday may not get you a lot of business. However, an update a few times a week that covers developments in your field may be just right – even though it is less frequent. If these updates are short, use Facebook or Twitter, where brevity is the rule.