"Remember Me" Cookie Exists, but Users Still Getting Logged Out

This web application is using forms authentication and a LoginView. When users select the "Remember Me" checkbox when logging in, the user is supposed to remain logged in for 30 days. This is being set in the web.config file:

<authentication mode="Forms">
    <forms name="RememberMeCookie" timeout="43200" slidingExpiration="false" defaultUrl="~/AccountHome.aspx" />
</authentication>
The cookie created from this is set correctly. However, about 24 hours after logging in I'll find myself logged out and forced to log in again, despite the fact that the RememberMeCookie still exists. Other users have reported the same problem. Is there some other application-wide setting I'm missing that would cause this problem?


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