Angular is a fast paced technology with a new major version every 6 months. PrimeNG release cycle is aligned with Angular and every 6 months a new major PrimeNG version is released that is compatible
with the latest Angular core. We are aware that majority of the existing applications prefer to remain at a previous version due to stability requirements instead of upgrading to the latest version immediately.
PrimeNG LTS is an annual subscription based service to provide a license for the finest compatible version suited to you. LTS covers the prior two versions from the latest release, this means up to 18 months
of almost weekly releases to bring the latest defect fixes and security updates to your project. As an example, when PrimeNG moves to Angular 9, PrimeNG 7 and 8 will move to LTS support whereas STS (short term support) versions of PrimeNG 9 will be open source under MIT license for at least 6 months until PrimeNG 10 is released. Here is a timeline to visualize the LTS support.
Please visit the LTS page for more details.