This differs for different parts of your website. For instance, your content you can update as regularly as you feel suits your brand and messaging. Customers enjoy new, fresh content so you need to simply establish the frequency of your updates. Most websites have a blog page and this is where new, relevant content can be added to your website and most brands post weekly updates. If your content is optimized your organic search ranking will improve too. When you consider your security and functionality on your website, you usually have to update these every couple of months. Or when a new feature is required to ensure your website is compliant with search engines.To establish the frequency of these updates speak with your design and development team. They will check the health of your site and ensure all links and functionality are working correctly.