We start making sure our application runs on the next version around the time Beta 1 comes out. We upgrade the development environment around the time when our

We start making sure our application runs on the next version around the time Beta 1 comes out. We upgrade the development environment around the time when our tooling (phpstan, cs-fixer) runs on the next version, but doesn't necessarily support new language features. We upgrade the production environment when our tooling supports most of the new language features and at least all of the ones we want to make use of. This usually happens within 3-6 months of the release. By that time the version has stabilized enough to be safe for production use.