I think it is important to distinguish between people who are likely to commit serious crimes against persons and who constitute a real danger to society, and people who will commit further offences—including some of those on your list—but who do not pose a serious threat to the public. All of the evidence indicates that violent crime is less prevalent amongst those aged over 35 or 40. Furthermore, even if they are still numerous, there are far fewer people over 40 being sent to prison than there are 20-year-olds. In my opinion, only a small percentage of offenders convicted for a third time will go on to commit serious crimes against persons.
On November 15th, 2007. See this statement in context.