Wouldn't you just know it? - I'm going to disagree with both of them
It all depends upon what you're trying to do. The whole point of the "fermentation on the pulp" business is to extract colour and flavour. Alcohol is better at this than water, so the longer you leave the fruit in there, the more colour and flavour you'll get. But that has it's own downfalls, because there are many more flavours there than merely the ones you want to extract - elderberries, in particular, are high in tannin, which tends to turn the inside of your mouth into a furry moonscape. Then again, tannin aids tremendously in maturation and preservation. So - what are you after?
Let's do them one at a time, starting with the "don't leave for more than a day" merchant. Well, what's the point of putting the fruit in there at all? In one day, very little alcohol will have formed, very little dissolution of pigments and flavour-enhancing substances will have occurred - very little of anything, in fact, will have happened. What an utter waste of a day!
On the other hand, 8 to 9 days is an awful lot. Tannin extraction, especially with elderberries, will be maximised. That's going to mean a beautiful wine in ten years' time, but it's going to be undrinkable for at least three years. If that's OK, then fine - I don't want to wait that long. Besides which, the increased risk of infection of the must with all of those solids hanging around is too much to take.
Last year, I made a very decent elderberry wine (at 4 lbs of fruit per gallon) which was drinkable within a couple of months. It had 4 days on the pulp. I do not believe that the flavour could have improved with a longer pulp fermentation period.
That, then, is what I advise - 4 days, modified by ... 3 days on the pulp if you're after a light-bodied wine, 5 days on the pulp if you're after a long-term keeper. And that applies for any fruit, not just elderberries.
Hope that narrows it down a bit for you.
Mike
