[AaronI]

They can pass an act designated as "private law" (aka slip laws), which can apply to specific individuals and afford relief from another law or grant benefits/powers that are not available under the general law. So Congress actually does have the authority to extend his tenure.

[davetufts]

Your example requires that Congress pass legislation, which is exactly what I'm making a case for. In practice, and after reading this article, I doubt that will be the way it goes down.