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You choose how long you stay signed in — 6 hours, 1 day, 1 week, 4 weeks, until you sign out, or a length you type — and you can change it on the account screen.
Until now every sign-in ended after 24 hours without use, for everybody. The sign-in screen now has presets, a slider and a number with a unit, all pointing at one value, and the account screen shows the current choice with a Change control. Whatever you choose, the server asks for a fresh sign-in at most every 30 days; a remembered device signs in again by itself. The Privacy Policy's retention row for sessions says this in version 2026-09-07-v16.