depends on the strain, youll usually want to flower for atleast 55 days - but some strains go 65 and 75 and ive had Island Sweet Skunk go all the way to 104 days til it was ready! use this trichome chart to determine when your crystals are ready. its all about what type of high you like, cloudy crystals will give you a sativa-like headhigh, and amber crystals will give you a narcotic couch lock indica-like high. i like about 60/40 cloudy:amber, but its all about what you like. now that ive stated that crystals (trichomes) are the most important factor in determining ripeness, its also good to be aware of the hairs - you dont want white hairs.