Name the return, not the open
When a release renames a feature event, every retention report that keyed on the old label goes quiet.
Teams often treat retention event names as disposable labels. A designer renames a saved-project screen, an engineer ships a new habit loop, and suddenly open_home and resume_work both exist for the same moment. Reports that once looked clean become archaeological digs.
Prefer verbs that describe return intent—resume_project, complete_weekly_goal, reopen_draft. Keep platform out of the event name; put it in a property so iOS and Android stay comparable. Write allowed properties on the same day you create the event.
In Retention Signal Inventory engagements we spend the first day on inventory alone, because until synonyms are visible every later fix guesses at the wrong root.