PMC Post Savior checks every 15 seconds to see if you’re still logged in. If you are not, it presents a pop-up window so that you can log back in without losing your work.
Github: https://github.com/Penske-Media-Corp/pmc-post-savior
WordPress.org: https://wordpress.org/extend/plugins/pmc-post-savior/
Image by The Library of Congress. See link for details.