Pragmatism v. Rights

When parole was abolished in Virginia there was an estimate that the prison population would rise to 49,000; it has only risen to 35,000+. Now, Virginia still had to build 8 new prisons and it is a population increase of 8,000+. Still, it's an interesting fact. One of the reasons given for the lesser growth?

“It’s worked well because it was based on a fairly simple premise: Most serious crimes are committed by people between the ages of 18 and 32. If you make the penalties so harsh for a first offense for violent crime that they get taken out of circulation, by the time they get out they are older and less likely to commit a new crime.”

And I think that is a fairly accurate statement. Common experience tells us all that males tend to mellow with age. Very few men will do the stupid things they did when they were 18 once they hit 30+. Energy and aggressiveness fades over time.

The question then becomes, should prison time be keyed to age and gender? More importantly, can prison time be keyed to age and gender under the constitution? On the one hand, if age and gender determine length of sentence we move beyond punishing a crime and punish status. On the other hand, if an 18 year old male charged with an assault is 5 times as likely to offend multiple times in the next 5 years than a 35 year old woman charged with assault, is it just to ignore their statuses? (stati?)

I look forward to your comments