Check on the day of release. For Virgin that's 330 days in advance, for ANA that is 355 days (I think) in advance. For non status holders with ANA the inventory is basically the same as Virgin sees, so the benefit of booking via AMC miles is the earlier window. There is no magic formula other than book early, and then keep looking for additional releases as you get closer in. Also, be ready to send one passenger on other flights, ANA have more than one flight daily to some US gateways, but also potentially, use a different gateway