Ya when he commented on the NM's it made me think of "XI's Sky with Airships" lol Makes me wonder how many NMs they have planned and what kind of restriction they may set it place so that one group can't hard it.

Something that comes to mind is potentially money/time based with fuel consumption. When you find the NM location until you engage/beat it you have access to the location to defeat it but upon defeating it you have to rescout the area before you can go up against the NM again.