When you reach the higher levels of karma you no longer have to go through physical lifetimes to work it out. You can do it on the spiritual plane and still be working towards the ultimate. And even when you reach the ultimate, your karma will be influencing and including other universes and the working out of the complex tapestry of the universes. It is not to be considered a prison. It is just a natural cycle that you can grow and develop through to become your ultimate self.
