It can last forever. That is, if it kills you. Alcohol is a short-acting drug, but alcohol poisoning usually occurs at levels of alcohol of 300 mg% or more, often at levels of 500 mg% or more. This amount of alcohol will take 10-15 hours to metabolize. If that level, however, slows your breathing and eventually stops your heart and decreases oxygen in the brain, it can kill or lead to permanent brain and other damage.