How do you handle changes to courses?

We’re regularly updating our courses and so far, we are following this approach:

• we have created an additional free-text filed for courses called “Course Update History” where we add dated notes recording of all changes in a course. We make this field visible to users on the course page.
   
• if updates are cosmetic (e.g. branding, new screenshots, etc.) or very minor (like editing videos, removing parts no longer relevant, etc.) and don’t have actual influence on the knowledge, we simply replace the content.
   
• if the updates are more significant, but still and not changing the course completely (e.g. adding a video about a new product feature), we are adding new content and sending an email (from the Enrollments tab) to all people who Completed the course letting them know about the additional content which they can complete.
   
• if we’re building a completely new content, we’re introducing it as a new course and as above sending an email to everyone who is enrolled in the old version letting them know that a new version is now available.

I hope this helps and also wonder what others are doing.