This is why you should have repository manager like JFrog Artifactory or Sonatype Nexus which can transparently proxy third-party repositories (like Maven Central).
This is true for Maven. The Maven repository project is very impressive and outstanding in its kind anyways. But leaving this great repository you are often on your own. Look at what happens to Google Code. How much stuff will be lost when its shut down? Hopefully nothing that you depend on. Its nice to have the binaries in a backup maybe but without access to the code, maintenance will be a nightmare.