From my experience, the animal will become quite hungrey if it does not feed for a week Pacing and exploriation will increase and there is a greater chance that the animal will try to escape or do something else risky. I'm not saying it will perish, but you are taking an increased risk. Adding prey would probably help, but there is also risk to this action. If the animal kills more than it can eat, there is a chance that the water will foul.
Octopus are not like fish. You cannot hook up an automatic feeder. It would be best if you could get someone to come in and drop in a few snails or hermits mid-week, but if not, your chances are still good that the octopus will pul; through.
Roy