From what I've been able to gather is that a fleet can operate anywhere within it's assigned naval bases AOR "area of responsibility" when it's on mission it's supplies determine exactly how long said fleet can remain on mission. This makes sence in that a fleet can only survive so long on it's perishable goods. What doesn't make sence is why if a set a fleet to patrol a system with an established world why can they not replenish there goods there. It would also make sence that a fleet close within an AOR of a navy base no matter what it's doing recieve a steady stream of supplies from the base. To me only fleets that operate outside the realm of there AOR bubble should have to rely on supplies carried with them. It doesn't make since that a fleet with a full load of supplies cannot travel outside of it's AOR bubble.