Ok, to help you with your scenario, I just implemented a new web.config setting. If you put this in your user.config file, then after upgrading to the next release, the remember me checkbox will not be shown on the login page but it will function as if it was checked, ie a persistent cookie will be set.
<add key="ForcePersistentAuthCheckboxChecked" value="true"/>
So this will work after the next release, or if you make your own build from the source code repository it is available now.
Hope that helps,
Joe