practice.json beside a preview holds the day it ends. The cleanup decides by these rules:

Situation	Result
The issue is closed	The preview is removed at once, without a note
The day has not come	The preview stays
The day has come and a person has given a thumbs-up (`term-keep-reaction`)	The preview stays until the issue is closed
The day has come and there is no thumbs-up	The preview is removed; the note in the issue mentions the issue's author (login from the API, only letters, digits and hyphens) and asks for feedback
The issue no longer exists	The preview stays until the day, then it is removed without a note
The folder has no readable `practice.json` for its own issue	The folder is removed at once

Every write of i/ on gh-pages is one new commit without a parent, pushed with a lease against the state it started from, so that a removed preview is in no history of the branch; a lost lease repeats the change. The deployment of the site and the pull request previews add ordinary commits and leave i/ as it is. The length of a preview, the schedule and the dry run are in docs/lifetime.md.