I just want to make absolutely, positively, 110% sure that this is optional. That the pair on duty do not have to interact and they are not required to respond to anything that happens. You can still have a life and if you're busy on that day, that's totally fine.
And I also want to reaffirm that this is not the IC methodology of doing things. ICly, several people have several-hour shifts every few days; there isn't anyone who is ICly required to patrol 24 hours in a day. This is just a convenient OOC way of saying "If something happens today, Flynn and Aqua are the default characters who will respond. If Flynn and/or Aqua doesn't want to, we'll take volunteers or roll again."