[Fedora-packaging] Where Can I Find Previous Versions?

I've noticed that mirrors no longer appear to contain previous versions of packages. For example, when kernel-3.4.3 was released, kernel-3.4.2 disappeared from all the mirrors. I recently had regression troubles, and I wanted to downgrade to a previous version to resolve the issue. However, I was surprised to find the previous version was gone. My only option was to downgrade to the original version that came with the distribution. I was very disappointed with that. Is there some place I can find the previous version? If not, is it possible to change this so at least 1 previous version is left in the mirrors? Joseph D. Wagner