It seems that users have to repeatedly log into the web app even though the selection below has been made on the login page.
How does this "Keep me logged in" feature actually work? Is there a time limit based on cookies (or similar) for how long the login is valid?
This will save an authentication key to the "local storage" of the web browser. Anything saved there has no expiration time. Unless you open the page in a "private" or "incognito" tab, in that case it does get cleared when closing the page.