This is definitely a great concept, but what would happen after his youth is restored? Would he become a fugitive again? It feels like getting his youth back wouldn't be the end of the story, but a secondary goal for something bigger (proving his innocence, maybe).
What are the obstacles for the protagonist? I think you need to include in the logline your idea about the experimentation that involves the government. Or at least mention that, in the process of finding the place where his youth can be restored, he'll put a top secret program that involves the government at risk.
As everyone else, I see great potential in an action film starring a young man imprisoned in an old-man's body. I would simply link the success of the protagonist (getting his youth back) with the opportunity to prove his innocence. Maybe that's the countdown's purpose: he must find the evidences of his innocence before the process becomes irreversible.
In any case, I'd love to see this film!