Rename pressure shows up after a rebrand or a new PM. Without a version rule, every rename forks historical reports.
Prefer additive properties with a deprecation window. Keep the old key emitting for one release cycle while dashboards migrate, then remove it on a dated ticket.
Identity keys need the same discipline. Mixing anonymous device IDs with logged-in user IDs mid-funnel is a common way to invent phantom drop-offs.
A one-page schema charter beats a 40-page wiki nobody opens. Owners, naming pattern, and change process — that is enough to start.