no hard and fast rule about how many or when. With most routes you will find have that an initial few will drop in 353 days out, and then more may be made available if the airline feels that the flight is selling below their expectations. The airlines want to make sure that the flight leaves full so if sales have been slow they’ll open up more, however if sales are strong then unlikely they’ll open up more.
With lord Howe it is a little different, as qantas basically has a monopoly on the market out of both Sydney and Brisbane. Lord Howe is a very popular and beautiful spot, and given that only qantas fly to or from the island you might well find that they’ll never open up award space. Given qantas’ position in this market, they may quite rightly feel in a superior bargaining position and know that the demand is there and that if they leave it people will pay the asking price and the flight will go full.
It sucks but I reckon the only chance your points have of doing you any favours here is with an anyseat redemption, which is appalling value for money. This is a common issue that many have griped about, both here and on other forums and sites before, so I wouldn’t hold out too much hope.
Only thing you can do is check religiously, and hope for the best.