Probably about 5 nights a week, but of those 5 only 2 or 3 will I drink enough to result in a noticeable hangover ( usually about 6 - 8 pints, dependant on how much I've eaten ), which invariably lasts from a few hours to most of a day. It doesn't prevent me from doing what I do, or my work but I'll be honest it can affect my concentration or efficiency.