In Norway the maximum you can be jailed for is 21 years. The idea is that you're not the same person you were 21 years ago, and prison should focus on reform not punishment. Norway's first terrorist who killed 93 teenagers is serving his 21 year sentence now, and that is challenging the Norwegian view of justice. However, if a prisoner is deemed to still be a hazard after that time the sentence can be extended, and that is what will certainly happen in the case of the Norwegian killer. I don't know if France has something similar. Given that the man in this story is 75, we could hope he will finish his days behind bars. The article says in-between his killing and justice he was accused of several other rapes by the same method, injection, so he certainly hadn't changed his ways over the decades and there seems to be no good reason to think he will.