Okay here's again a question for the experts.

I have an upcoming trip connecting in DXB, which I want to upgrade.
While there is no availability on the first leg currently, there is on the second.
I would however like to upgrade the whole trip (two segments).
According to the mileage calculator the difference between upgrading the two segments seperately is more expensive by 5k miles, than to upgrade it as a whole.
So now I am stuck between
- securing at least one upgraded segment, but that might be more 'expensive' if the first segment also clears
- or waiting for the first segment to become available and save 5k, but risking the (currently) secure upgrade on the second segment.

Is EK customer-friendly and charges only the cheaper 'whole upgrade rate' if one segment was already upgraded in advance ? Or do they simply charge in such an event segment by segment ?

Cheers
TheAirman