I think the idea of punching down is to improve extraction of compounds from the skins, so more punch downs usually means increased extraction. There are a lot of details to consider: at what stage is the fermentation? brix?, if you cause the skins to turn to pulp, you'll have trouble pressing and most likely lots of fluffy lees in the secondary. Are you sure you want to extract everything from the skins? Even bitter compounds? This depends mostly on the fruit quality. How much oxygen are you incorporating during the punchdown? In small quantities oxygen is beneficial, but too much at the end of fermentation may not be so good. I've read data that suggests that a fermenting red wine needs 2 to 4mg/l of oxygen twice a day, so I drain the wine through a venturi and return it twice a day, but I certainly don't know how much oxygen I'm incorporating.
