Microsoft Dynamics CRM is a continuous book, with pages being edited and new pages being added with each release. Those who build their projects to live with the growth of their companies do not need to be concerned for the book continues as your business continues.
For those who are still running Microsoft Dynamics CRM older versions, this page might be of interest. The Microsoft Support Lifecycle Page
What is a Support Lifecycle, you ask or more appropriately, what is the support lifecycle policy? There is more on the website, but consider this ...
"What is the Support Lifecycle policy?
Microsoft provides an industry-leading Support Lifecycle policy—in length and provision—giving customers consistent, transparent, and predictable timelines for which software is supported."