Hello,
Well recommended is a big word, some studies ensure that 48h of darkness before cutting the plant gives an higher thc level, if it works, not sure, some says it does some it doesn't, i tried it some times but ofcourse im a regular grower so i cant say if it worked as i never took my buds to analyze in a lab, some people also give them ice cold water while flushing, but same story, not sure if it works