I think JAL domestic flights only become bookable 2 months before. I vaguely recall reading about this a couple of days ago. I'll check where I saw it and get back to you.
Now I know where it came from:
http://www.britishairways.com/travel...d/public/en_gb
Redemptions on Japanese domestic flights may only be booked two months from the date of return flight and only in the economy cabin. This restriction does not apply to domestic flights booked in conjunction with international flights.