On a TATL segment you will get a drink service before dinner, then a top-up at dinner. There may be another service mid-flight (usually not on the US-Europe segments given the time and desire to sleep). You will get an opportunity for one more round before landing.

If you want more either go to the galley or push the FA call button. Since booze is free in all cabins on TATL there shouldn't be an issue getting an additional drink at any time.