I would agree that the focus needs to be less on punishment of vengeance for the victims, and more about preventing future crime. For some people, prevention of future crime probably really does mean that they spend the rest of their life behind bars if they're allowed to live at all. People like Ed Gein, Ted Bundy, Charles Manson (Who by the way is still alive), etc. For others, a different approach is definitely needed. Sticking an 18 year old kid with no prior history of crime in a cage with rapists and murderers is a definite way to ensure that he'll never be reformed, or a productive member society again. You're ensuring he WILL commit crimes in the future.
First and foremost, however, I think the most important thing is that as a society we address the problem of, "victimless crimes." No one (in my opinion) should ever be held in a cage or at gunpoint if they haven't harmed, or stolen from another human being in some way (things like breach of contract and white collar crimes can still count as harm and theft), or if all parties involved were consenting adults.