Comment by WorldMaker

The version increments roughly every 6 months. It's almost the exact same update cadence as NodeJS: LTS versions are even numbers released in the Fall and STS versions are odd numbers released in the Spring. STS often focuses on "bleeding edge features" and LTS often on performance and stability. (Though both are year round projects and there are bleeding edge features in an LTS and perf/stability fixes in an STS.)