As far as I know, lifecycle is still the same as the main Fedora lifecycle of one year from release. Part of this is that there is a lot still going on in setting up the Server group. Trying to add in extended lifecycles and such would happen after the basics of what was in Fedora Server were in place. It also requires users like you to explain what they want in an extended lifecycle and what resources they are going to bring to help meet those needs.