Beginning with 4D v18, the naming convention and intervals of our product releases have been changed:
1- The R-releases will now be referred to as “Feature Releases” and they will continue to be released every three months.
2- And the 4D v18.x releases, will now be referred to as “Long Term Support Releases” (aka LTS-Release).
That being said, starting with 4D v18, the release interval will be extended to 24 months to give you more time to use and deploy a version. Support time will be 36 months, giving you a full year following a new LTS release to migrate from the previous release.
Please refer to this https://blog.4d.com/4d-product-release-cycle-everything-you-need-to-know/blog post> for more information about the new 4D Product Release Cycle.