Some object that a 180-day feast seems to be an absurdity, but note that what is done for 180 days is not just feasting, but "showing the riches" of the kingdom. This type of event (which fits in well in the known secular chronology with Xerxes' attempt to drum up support for his war against Greece by putting together a 180-day display of his wealth prior to submitting the war proposal to his princes, as was reported by Herodotus) suggests a rotation of nobility coming in to be wined and dined at the expense of the king -- it does not suggest a wholesale abandonment of administrative posts by all invitees throughout the empire for a period of 6 months.