Leaving the plants in darkness for a period of time before harvest does increase the plants trichomes and doesn't contain any excess starch/nutrients. It has been proven I think. I watched a video of a guy who did a test on 12,24,36,48 hours 72 seems very excessive to me. but he did say the 12 and 24 had a considerable impact on terpene and thc% content. But after that the thc dropped slightly. Bear that in mind, I always do mine for 24 hours.