You want to ensure that you are the go-to source for information on your industry.

How often you update your news/blog section can vary between businesses based on a number of factors, including but not limited to:

• Time available to dedicate to writing
• The expectations of your industry, for example lifestyle or fashion updates would be expected at a daily minimum while a manufacturer's site might do with a post each week or two

If you are dedicated to maintaining an active news/blog section on your website to help keep current and prospective clients aware of what's going on in your business and industry, you should try to add new content at least every two weeks. Much longer than that and you run the risk of your news becoming stale and readers getting their relevant updates elsewhere.