I am the designated driver often. I just weigh a lot and don't drink very much. Last year at Wild Brew I tried about ten beers, but only had an ounce or two of each. I drank diet soda for the last two hours before I drove.
I just don't ever get real drunk anymore. When I was a young man it was a goal many a night, but now that I am old, I just can't recover.
For me it was almost an instant change from when I turned 35. Before that, I could pull a near-allnighter and operate at work on 2 hours (sometimes less) of sleep by eating about 4 aspirin right before I fell asleep/passed out.
Now, the goal isn't to get drunk, but to 'relax'. Typically, the hardest drinking I will do involves friends' birthdays, an establishment just south of the I-44 overpass on Sheridan, and a lot of glitter. I haven't done that in over a year now, and I really don't miss it (the drinking part that is).
I have to be careful; my father was an alcoholic, and I know there is that propensity for it to be genetic. There are weekends I can polish a six-pack of Marshalls off in one night. Then I go through times where a six pack will last me two weeks or more.