The "screwing with it" does not take much time. Building the binaries themselves do. Mozilla does it few days in advance, so at the release they can push every

The "screwing with it" does not take much time. Building the binaries themselves do. Mozilla does it few days in advance, so at the release they can push everything (and the binaries are available on the ftp.mozilla.org day before, uusually around 16:00 UTC). Other parties can start building their binaries only after the release. In case of Fedora, it is pushed into the testing stream and only after positive feedback (or few days) it is pushed into the release. If you want it earlier, you can get the tested builds from bodhi (bodhi.fedoraproject.org). You can also see the status of all builds there.