This depends on your business, but in order to have the best results in Google search results, we recommend keeping your website current. Google tends to ignore sites that get ignored by their owners.
If you blog, a small business can do so once or twice a month, a medium-sized business may want to update once or twice a week, and for more competitive industries you may even consider blogging daily.
Also, think about your customers—they want to see relevant information that is up to date. If laws, products or information changes, make sure your website reflects that.