There isn't a "far ahead" date for booking the (few) routes and dates that are zeroed out -- there are no seats to book, ever, so it isn't competition with other people booking the seats before you, but rather the airline making none available. This is due to the high demand for more expensive tickets during the current airline boom. It will end, as booms always do, probably with a big bust, but probably not in 2007. Hard to say how the year will go, but probably with worse supply as the year goes on, so book what you can.

The exact formula for OWE fare allocation is a trade secret, but the "over ocean" routes get the lion's share of the fare. So 3 sectors out of the 20 get more than half of the ticket revenue (or 5x the revenue of the other sectors). Thus the airlines all want to fly trans-Atlantic, trans-Pacific and Europe-Asia/Australia on these tickets. Some similar length/service flights, such as LHR-JNB or JFK-EZE get far less, so it isn't a fair division, but the airlines made up these rules. Again not enough of these tickets to really matter, so the airlines leave the system as it is.