I think my son's drinking habits are very much like you describe too. He goes for a long workout first thing and then begins his practice at noon until evening and I believe he begins the drinking early evening, except at the weekends. There have been a few family parties on his father's side that he has attended and after both events he has been quite ill with hangovers and remorse over his drunken actions - that's when he's called me to talk and whine about that family. I did notice that it's either his cousins who are always drunk or his friends and their parents always falling about drunk and never him. His grandparents live next door to him, so it's very easy to go and have dinner with them, knowing that wine will be served and he can always sneak down to the cellar for a bottle that they won't notice is missing. Then of course his father takes him out at weekends for lunch and a few beers - the man to man thing. I am the last resort I guess. When all else fails call mum and ask how she is, test the waters and see if asking for some cash is a possibility or agreeing to meet up and then get the cash.
I see the pattern now quite clearly. I can't change the other's actions but I can and will change my own. It's tough love for me.... one day at a time.
Thank you for helping me understand the importance of this tough action.