I think we set an expiration date because we knew when she'd turn 18. There are a few bans like that, I think.
Do people with an expiration dated ban, because of age, receive a notification email: "Happy Birthday, and welcome to I2"?
No, I don't think they do. The ban simply expires.
I remember we had a discussion about this a long time ago. It would be nice if the board software would automatically send the person a reminder, but it isn't possible without some tweaking.