18 - 21 I never had hangovers, I could drink as much as I want and within an hour of waking up I was fine. As soon as I hit 22, if I have more than 3 or 4 few pints I wake up with a thick head, but I don't drink anywhere near as much as I used too.
Hangover ritual now is get up early no matter how bad I feel, pint of water before bed, pint of fresh orange juice as soon as i'm up and toast. Then if I still feel rough go for a walk to clear my head.
No matter what I do I feel rough all day though, dam you age!