How to you handle the end of life (EOL) of libraries?

In the past I've worked on new library launches, major upgrades, and I'm actually in the process of an end of life (EOL) effort right now. While these types of efforts have their own nuances, the core principles remain the same. 

1. Transparency - When working on developer tools you have to maintain the highest level of transparency possible. Systems, developer workflows, and customer data can all be dependent on these tools and their interfaces.
2. Communication - The way and the cadence that you distribute information about changes to libraries or tools goes hand in hand with transparency. You need to ensure that you are giving your end users enough time to adjust/migrate, test, and be confident in using the next version or tool in a production environment.
3. Cross Functional Teamwork - Assembling a group of team members from across the organization will ensure that you are considering the customer/developer experience as well as any edge cases. Working with a team like this enables you to be really thoughtful about what to communicate (transparency), and when and where to share it (communication). I like to keep a group like this going even after a launch or major change for a little while so that you can hear feedback and areas to improve.