Heroku Play - Version lifecycle

Version lifecycle and lifecycle policy of Heroku features were not captured when implemented, meaning we have been caught-out more than once when something is reaching end-of-life/end-of-support (most specifically, Heroku Stack and Play).

Where can I find the lifecycle policies for both, including: version release date, end of support dates (including announcement date), and how to be kept informed of new announcements/upcoming end dates?

Thanks

Have searched through Heroku documentation online, but results haven’t been helpful.