The usual advice on this forum is to book very early for QFF seats particularly if you are looking for seats in the high/shoulder season.
However, you can get lucky. My wife decided yesterday to travel to Indonesia. I had previously checked QFF seats two months ago and there were no seats after 5 December 2007. I checked last night and there was a seat on Friday 14 December 2007 - SYD/JKT leaving on 14 December 2007. This morning I tried to book that seat and I found another seat available on 12 December as well. Anyway, my wife is now travelling at short notice using QFF for all flights - SYD/JKT return leaving on 14 December 2007 and returning to Australia on 31 December 2007.