I booked award tickets for travel to NY on 23 Jul (Prem Economy) on the first day they were avail (the 330 day mark). I booked them one way, knowing that if I waited 3 weeks for the return leg to be avail, the outbound awards would be gone.

The return leg from MIA never seemed to show any availability. I phoned Virgin as was told it was possible there wouldn't be award availability for MIA (and ORL) during the peak summer months. It depends on how much space is left on the flights.

At he time, I noticed that there was an award sale from BOS and availability for mid Aug. I booked those. It was cheaper to buy the internal flights to BOS and stay there for a couple of days than to pay for return tickets. So we have an extended holiday. :-) I think the trick is to be as flexible as possible with the tickets.