Dosage and frequency are 2 different things.
Smoking a pack of cigarettes every year wont kill you, but smoking one cigaratte a day for a year might.
My intuition would be the opposite of yours. I think our body is reasonably well equipped to handle low dose exposure, but large doses at once are more likely to cause irreversible damage.
Is a pack of cigarettes high enough to kill you if you smoke it all at once ? I know quite a few friends who get through a pack a day.
I didn't say 365 cigarettes at once. Everyone knows its too high a dosage that might actually kill a person, just like a high enough dose of caffeine or alcohol.
I don't think a cigarette a day is low dosage. While you might not die of a heart attack or get lung cancer directly from smoking, it might still increase the risk of serious diseases given other environmental conditions, your fitness level, diet, etc. The 2 drinks a day has to be seen in a similar light.