I say, cap them at 10, make prison compulsury college, and bring back capitol punishment for eggregious crimes of an unforgivable, or irredeemabe nature. If a decade is not enough to learn, I doubt and extra one will help. Much less an extra decade being treated like meat inside a cell. Prisons are just places to hang out and learn from other criminals, while sowing distrust for authority right now. Precious little rehab is happening behing bars, and more trama than can be counted. It is well documented that trauma leads to more violence, and the cycle repeats. Either we start treating prisoners like people, or justify the current system of incarceration some other way.
I realize capitol punishment is unpopular, but there is some validity to deterrance, and life behind bars, unless things change, seems even less humane to me. I welcome a better solution, but what we have now seems ancient and barbaric compared to the rest of the world we have created.