When a test produces an output state (cookies, local storage, IndexedDB) that downstream tests depend on, that state used to expire after a hardcoded six hours. For some applications six hours is fine. For others (long-lived sessions, daily test runs, slower QA cadences) it forced unnecessary re-logins.
Output state validity is now a per-application setting, configurable from 5 minutes up to 7 days under Project Settings → Applications → Edit → Session State Lifetime.