Confirmation, as it has been practiced for a long time in the Episcopal Church, will not bear much rational analysis. When one tries to read about its theological rationale, there isn't much to read. No one can really think a twelve year old confirmand is making a mature or "adult" re-commitment to the vows made on their behalf at Baptism. More likely, they get confirmed because everyone else is doing it or because parents and clergy make it known that it is expected, which is to say, not optional.
Some years ago, in spite of spirited opposition, I made 18 the age of confirmation in parishes I served. And that after two years of preparation in Scripture, theology, church history and practices, and some ethics.
Even at 18, I still wonder if the confirmands are clear about what they are doing, since the years that follow tend to be the ones in which they are most absent from participation in the life of the church.
It seems worth while to ask whether when we "confirm" someone, anything is actually being confirmed.