End of life dates

• Major releases, such as 3.0.0, 4.0.0, 5.0.0, and 6.0.0, provide an opportunity to introduce non-backward compatible features.
• Maintenance versions, such as 4.1.1 and 4.1.2, are only used to fix problems. Maintenance activities occur on all releases but are primarily used to determine how long maintenance is provided for a particular branch of code through a tributary release of a minor release (for example, 4.1.x). Active maintenance on minor releases means that we fix some bugs and migrate some fixes back to the code branch.