You set how long behavioural data is retained in Settings → Account & Settings → AI & Privacy. Your plan sets the ceiling on what you can configure — from 30 days up to a year.
What Deletion Leaves Behind
Retention deletes events, not people. A person whose events have aged out keeps their row, but with nothing attached — no pages, no sessions, no device or country.
This is why visitor lists are windowed on last seen rather than first seen. It also means a very old contact can look like a tracking failure when it is simply a completed retention cycle.