Full reward flight. Best way to book

Half way through our holiday and planning for next year.
With upgrade reward rates going up I'm considering full reward flight for next year.
I already have enough miles and expect Mrs D will soon.
So the question is: Should I book the outbound leg as soon as it is released, or rather as soon as any Upper seats are released and then wait to book the return. Or should I wait and book both ways?
In the past with upgrading I've always booked a return flight as soon as the home leg was released.
I'm planning to do LHR to ATL this time.
Dick D
With upgrade reward rates going up I'm considering full reward flight for next year.
I already have enough miles and expect Mrs D will soon.
So the question is: Should I book the outbound leg as soon as it is released, or rather as soon as any Upper seats are released and then wait to book the return. Or should I wait and book both ways?
In the past with upgrading I've always booked a return flight as soon as the home leg was released.
I'm planning to do LHR to ATL this time.
Dick D