I disagree. On the shelf has many different meanings. In the life retirement isn't used as word...you can't retire. Being put on the shelf can easily be due to old age or many other reasons not exclusive to punishment. Whether he got out on is own is a different story, but i would speculate to say that someone eased him out because of the fact that his brother died and without the chin around mario was probably useless and more importantly powerless.
I've never heard the term used in any other way. The implication seems to be one of punishment. A guy that gets put on the shelf has done something where he more or less loses the recognition of being a made guy and the ability to continue in family-sanctioned operations. Though, like with the Colombo brothers, there may be exceptions. But I don't see Mangano being put on the shelf by anyone. And it's not a matter of him officially retiring or leaving the mob. Just more or less being inactive. At least in the day to day sense.
