There's a call button at every seat, you don't (usually) have to find anyone. I think proactive drinks service should be done at least once an hour, but as long as the crew is responsive to the call button and doesn't make a fuss about bringing me another drink, I'm okay with it (but it doesn't feel very premium). On those few flights on TK, I never had a problem ordering few rounds of drinks this way, even though they were fairly short flights.

My bigger problem is the coffin flight concept with blinds locked throughout the journey. I'll be doing the same flights as the OP and I can't imagine spending 17 hours in darkness on a flight departing 8:30 and arriving around 19. Based on reports from others they usually do unlock your blind on request so I hope it will be the case here, otherwise it's gonna be a torture and I'm gonna need many drinks to get through that