I have enabled the Discussion notification on Open unanswered questions on the forums with age > 48 hours.

I get a mail alla this every 4 hours:

You are subscribed to an email alert for unanswered discussion questions. The following questions have not been answered in the last 48 hours:

• bla
• bla

I can't see any option to set the frequency of this notification, but every 4 hours is a bit much.. once a day/once a week would be more appropriate.