Ronin, take a look at the Form of the Self-Registration page. There is a field called expire_after which is hidden by default. The initial value of this field is the default time in hours for expiration of a guest account when Self-Registration is used. If you are using the manual 'Create Guest Account' menu you can define a custom expiration.
@Ronin101 wrote:
Dear Tim,
Can you point out where we define guest account expiration