Question:

At what age does a Jewish man have his second bar mitzvah? Is it any different than the first time around?

Answer:

Though some people symbolically celebrate a second bar mitzvah at a later point in life, the bar mitzvah essentially marks the day someone becomes obligated to do the mitzvahs. This happens on a boy's thirteenth birthday, whether it was celebrated or not. This is the meaning of the word "bar mitzvah"—a man bound by the mitzvah.

It follows that once someone has passed that age, he is "bar mitzvahed" until the final day of his life. This is something to celebrate every day – the fact that we were enjoined by G‑d to be bound to Him through His Torah and the commandments.1

But some people like to celebrate again, often after a period of spiritual reawakening and rededication to Torah study and observance. So they choose a milestone birthday when they are once again called to the Torah, and they read the Torah portion that they read on their thirteenth birthday (or the Torah portion that would have been read on that date). Now this is a fine idea, but not at all obligatory.

Another bar mitzvah milestone is the mitzvah of tefillin. We begin wearing them at age 13 and continue to do so every weekday from then on. If someone who became lax in his observance would like to rededicate himself to fulfilling this special mitzvah on a constant basis, and celebrate it as a sort of "re-bar mitzvah," that too is a good idea.