I've tried it with 72 hours of darkness before chop, 48 hours, 24 hours, and 0 hours, and it all looked 'bout the same to me. I mean, unless you do it both ways, you can't really compare. But I've grown the same strains so many times that I can compare pretty objectively, and I don't see any extra crystals or anything because of the extended dark period. In any case, it doesn't seem to hurt anything.