Flying CPH-DXB-NRT next week (Silver, Economy Flex). I have been quite lucky on this route in the past 5 months, getting op-ups on 4 out of 12 flights, with all of them being the DXB-NRT or DXB-HND flights.
Now here is the question. Other than tiers and ticket type, what are the chances of getting an op-up on the second leg of the flight if you upgrade the first? I have 45.000 miles to burn. I have been thinking about whether or not I should wait until I hit 55, and use them for an upgrade on the DXB-NRT route in the future, or if I should try my luck next week and upgrade CPH-DXB, hoping that it will give me an advantage when I am at the gate for the NRT flight.

Does anyone have any experience with this method? Should I gamble and sacrifice the 25.000 on a CPH-DXB upgrade, or should I hold on to them until I reach 55.000 and can use them for a DXB-NRT upgrade?