It usually stays signed in for months on end.
It happened a few times but all good for now.
I am signing out on laptop as well.
It can be triggered by app updates, cache issues, or Amazon revalidating two-step authentication.
The quick fixes are to update the app to the latest version, clear the app cache or reinstall it, and make sure your two-step verification method (authenticator app, SMS, or email) is set up and working smoothly.
Update the app.
My app started doing this about 4 days ago and my Mac started doing it yesterday. It’s kicking me out more or less every time I try to look at a different section of Seller Central it’s so annoying.