Think about applications, not one-off scripts. It should be easy to always stay on the latest language version, with good tooling to migrate your code, and importantly, the ability to do it piece by piece. (Python 3 was all-or-nothing for the entire ecosystem.) Also, many migrations are trivial in practice, like renaming an identifier to avoid the new keyword.

What this gives you is high confidence that when inserting a few lines somewhere, that fancy new for loop simply works. No need to scroll to the top if the file and remember which exact release of the 27 in the last year introduced the feature.