Jedi Master Mace Windu not available

There are usually 3-4 months between these types of events until after the first year when they become permanently available. 

Are you saying that since we were slow meeting the requirements, we need to wait a year before we can get him? 

Nope! After about a year it will become permanently available. Until then it will rotate in and out of being available for around a week about every 90 days or so.  Next one should be about two weeks away. There are sites out there that help track the days between events in case you get antsy.