Here's an excerpt from an online article I found:
To determine which type of drinker the patient is, observe his drinking patterns. If he is drinking more than two alcoholic drinks a day, he may be at risk for a lowered sperm count.
Time Frame
One study performed on male rats reported that the male sperm count in rats was decreased by about 50 percent during intoxication and the 24 hours after intoxication. Therefore, if an alcoholic or binge drinker is trying to conceive, his attempts will probably not be more successful than someone who only drinks alcohol occasionally.
Good Luck and Happy Baby Making! =)