Actually mold isn't much of a problem as the alcohol tends to keep the spoilage organisms suppressed. When you make a batch with fruit pulp, sitting on that pulp in the gross lees has a much higher chance for producing sulfur odors. It does not happen in every case, but when it does, it can permanently ruin a batch.
Also, extended contact with skins/seeds/pulp can add excessive tannins/phenols leaving you with a bitter/astringent mead.
It is safer to get mead off the fruit pulp as soon as you've extracted all the color/flavor/aroma.