It looks like airbnb does a good job updating theirs, but I can sympathize with the parent comment.
I've found coding style guides that end up obtuse, easily outdated, and arbitrarily fit to the preferences of it's creators. They often stagnate and are blindly followed just for the sake of following. A lot of the best practices in the document are things that should be screened for at the hiring stage, and many of the others are heavily debatable preferences that are only going to make a developer with an opposing opinion feel needlessly boxed.
Not that they are a bad thing and airbnb's looks really solid to me, but writing a coding style guide means you now need to maintain and curate it periodically – a process that is easy to neglect.
