I don't know about Il Mulino or some of the other non-Disney up-scale restaurants, but the 180 day rule is probably for 98% of the places:
Cali Grill, Jiko, Artist Point, Yatchsman, Narcosee's (sp?), Citricos, Victoria & Albert's, Flying Fish etc ...
Due to the dining plan + 180 day window, the days of spontaneous dining are quickly dissapearing