It's common to hear women say that they want to wean (or not breastfeed at all) because they miss drinking coffee, or want to have an occasional glass of wine, or don't like worrying constantly about everything they eat. Guess what? You can drink caffeinated beverages (in moderation), have an occasional drink, eat what you want and still provide your baby with the absolute best nutrition and immunological protection - mother's own milk.
But how do we know the donor has been "in moderation" and hasn't taken any illegal substances? Whilst I said before I wouldn't be averse to the occasional drinkie, but for me that's 1-2 a week, not 4-5 a night (as some people may see an "occasional" drink).