How long do nightmares typically last during alcohol withdrawal?

A week or less. Nightmares and vivid dreams can start in the first 1-2 days of withdrawal, generally are improved at 3-5 days and should be gone in a week. Appropriate medication, usually benzodiazepines, can reduce the complications of withdrawal. If this is you we are talking about, the major concern should be how not to drink any more. A counselor or your doctor can help. Very few people succeed on their own.
Alcohol withdrawal. This depends on many factors. The general health of the individual, the degree of addiction, the amount of alcohol consumed, the health of the organs e.g. The liver and the central nervous system etc., and the other co-existing diseases.