It completely depends on a case to case basis.
Those who commit murder, rape and other violent crimes, I feel should be given a heavier penalty.
Those who are career criminals should also be given harsher punishments.
Now as per the lesser crimes, I find that I view it as a mistake that was committed and they should be given a chance to show that they have been rehabilitated.
I would also factor in the scenario for why the crime was committed, for example if you stole food from a grocery store or someplace because that was the only way you could feed yourself or your family in a situation where say a disaster hit, then I see no reason for you to be given any real sentence, it was a matter of life or death and you did what you had to in order to survive.
I also feel that far too many people are given the label of prisoner, ex-con etc when they were wrongly imprisoned to begin with, I mean lets face it you can say you wiped a wrongful conviction off the record but when they get out in the community you can't wipe it out of the opinions, especially those that are deeply set in. You can't give the person the time and opportunities back either and due to that time in prison there are some opportunities that will never be offered them.
Even in regards to a person where you feel that the conviction was proper, I think that if the person shows that he/she has truly rehabbed then the case should be re-evaluated even when the time has not been fully served especially when there is no early release date set for good behavior, and the person given the opportunity to make a contribution to society.
As per the justification of punishment after release, people have their own opinions on whether the punishment fit the crime or not, in some cases there is also corruption where you'll see the politician or some other power broker want it to disappear so the person may be put in prison for a short time and the moment the public's focus is turned elsewhere even for a moment the person released for "good behavior". In that case I can completely justify punishment upon release even though it will almost never happen due to the influence of that power broker.
Also, while we're on this topic I would like to say Free Mumia!