We went for last Thanksgiving week, in the middle of June, and are leaving tomorrow back to Aulani. We made reservations 2.5 months, 2 months and 3 months ahead. We stayed in a regular Aulani hotel the first time and the Aulani DVC villas the next two times. There are still rooms available for our stay, but the construction going on right now might have something to do with it. We are not DVC members and did not rent points. When you check for reservations at Aulani and DVC rooms are available there will be a brown banner in the upper right corner for DVC villa room offers.
Also, since the reservations are room only, you can cancel at anytime up to five days before your arrival. They take a refundable deposit for the first night of stay. How long you book before for a 3 night stay probably depends on what time of year you go and how flexible you are about room categories. I just looked and there is still at least one DVC studio available Christmas week and spring break looks fairly open in all room categories. President's Day week is a little tighter but some choices are still there.
So, I would say for slower times start looking at least by 3 months out. For busier time, longer. For Xmas even longer.
