How often does Power Nap check for updates or back up? How often does Power Nap check for updates or back up?
Mail, Contacts, Calendar, Reminders, Notes, Photo Stream, Find My Mac, and iCloud Documents are checked every hour.
Time Machine backups are attempted hourly until a successful backup has been completed.
Software Updates are checked daily.
Mac App Store downloads are checked once a week.


Source: http://support.apple.com/kb/HT5394