Max, by career progression, I meant the ability to move to another type to get some variety. Trans Pacific flying is extremely boring and after a few years, most would be looking for a change.
Each aircraft would be able to do 3 return services per week so a fleet of 7 aircraft would indicate a capability of 21 services per week - that leaves enough down time for "A" checks but not enough for heavy maintenance but with brand new aircraft, the heavy checks are a few years off so there would probably be additional aircraft by then. Hopefully, for the crews, better destinations than LAX are planned.