yeah, I won't be "upgrading". I will just be installing a new version beside the old version. Then, I point the symlink to the new version.
But I won't always be installing the new version. I might be installing really old versions. Officially, we support two versions back, but I have no idea what that means with Apache. We all of these applications going to short release cycles, it's anarchy. Apache HTTPD moves at glacial speed though, which causes its own problems. I'm pretty sure we just support anything in the 2.4.x tree, but I really don't know.