I know several **heavy drinkers who almost never get hangovers, and to my knowledge are never drunk enough that they aren't in control of their bodies.
**"Heavy drinkers" is a value judgement of course. These people might just be considered regular ol' "drinkers" by some people. Six or seven beers every evening after work and eight or ten on weekend evenings is what I refer to.
I think it's relative. A six pack after work doesn't even approach what I would consider heavy drinking, unless the person is maybe 130 lbs or less. It's a lot more than I'd drink daily, but, based on my observance of others, I'd say a six-pack or 3-4 glasses of wine is pretty average. There are enough people that drink 12+ beers, a bottle+ of wine, or 500ml+ of liquor a day to claim the "heavy drinkers" name. Then there are the full-blown alcoholics who easily drink twice that much a day. There are also the people who claim they only drink socially, which may be true, but some do it two or three times a week and drink so much they pass out. I guess these are what you'd call problem heavy drinkers with alcoholic tendencies.
Enjoy your beverage of choice. Drink it responsibly. Don't run me over. Seek help if you think you have a problem.