When are award seats to Tokyo released?

I am looking at buying 3 business class reward tickets to Tokyo for early Jan next year, when I looked a few weeks ago there was quite a bit of availability when I went to book they had gone. Are flights added on a ad hoc basis, or are all flights added at the same time?

New availability can be added at anytime but in general, there will be a bunch of seats at the opening of the schedule and then closer to departure with a sprinkling of seats here and there between those two periods.