I dunno, does it vary with what you're drinking, or what you're eating, or some of the other usual suspects like how much water you drink?
One thing I've noticed lately is that sometimes a "tolerance for alcohol" is specific to what you built it on, as opposed to just the alcoholic content...I've gone to a lot of big Russian party meals with lots of food and a fair amount of shots (usually whisky...luckily Ksenia's grandfather digs whisky over vodka, so I don't feel like such an "Ugly American" when I prefer the former) and so now I'm much less affected by the shots--but I don't seem "better at drinking wine or beer....
Back in my college days ... the hangover was directly related to how much water & good food (fruits & veggies) I ate that day. Eat a couple of bananas and dring a couple huge glasses of water and I was good to go.
Personally, I think it's really one of the great mysteries that we will always try to solve but may not necessarily hit the mark, ever. . ..