Just booked LHR-HND in J class on JL, at the very end of the calendar (2024-Aug-01), for 70k Asia Miles. There's J space HND-SYD on that same day, but nothing leaving Europe the day before in order to get a through itinerary.

If tomorrow HND-SYD is also available, can I get them to add the sector to the existing booking and reprice as a through itinerary, and just pay the difference in miles (20k) and taxes (HKD)? If I can call right when it opens, within 24 hours from the original booking, does that make a difference?

Barring that, if something comes up with a full through itinerary EU>JP>AU, can they redeposit my miles while I'm on the phone in order to grab a new itinerary without losing the old one in the meantime?