@Corb_The_Lesser@talesofaprinny Nailed it. In this example, if you're on Fedora 40 you know that you have one month after the release of Fedora 42 to upgrade and stay on a supported version. That's why 13 months to give a little extra time.
What some people do is hang back one major release. So if you start with Fedora 40, skip Fedora 41 and only upgrade to F41 once F42 release. That way you're still getting new stuff to you every 6 months, but it's 6 months after it's been out in the wild.