We went through this last year--trying to book Dec 27-Jan 3 for Aulani @ 7 month window. We finally stayed in Waikiki until New Years Day, when our Aulani reservations started. We did find scattered days of different unit types for the few days before New Years Eve, but nothing ever opened up for Dec 31. The gigantic fireworks display that is put on at Ko Olina is now a major draw, so the night of Dec 31 is virtually impossible at the 7 months window. We were not going to stay at Aulani for Dec 28,29,30 and have to move out for the night of the 31st and then move back on the 1st--way too much hassle.
Our new strategy: just wait until about January 3-4 and everything opens waaaay up! Of course, if you have kids in school, that doesn't work too well!