what happens when Auto Increment reaches max value?

[Chris Bassett]

A few questions reagarding AutoIncrement fields...

What happens with a field marked as AutoIncrement reaches its maximum value? If you delete a row, does this allow another row to be added?

How can you go about freeing up "autoincrement" values to add more rows?

My concern is that usually when dealing with auto-increment fields, I just assign the largest possible numerical datatype (usually a bigint) so that I generally wouldn't have to worry about if all of the auto-increment values are consumed. But I'm thinking this can be problematic and a waste of storaqge when you have several tables (a few dozen) that are like this, each with perhaps a few thousand records in each.

What is people's logic behind using auto-increments and chosing the proper data type for the column?