Though our kind of Cannabis is for the most part a domesticated plant, it still retains many of its natural self-defense mechanisms. One of these is the extra release of trichome resin during dark periods. When it gets dark, the plant begins to produce potentially up to twice as much cannabinoids than during daylight hours as the result of this heightened resin production, and as the late growing season progresses, daylight hours begin to wane, extending the dark period by about two minutes every night. Theoretically, these waning hours of daylight are ideal for extra resin production. A gradual process is much better in my opinion than sticking the plant in the dark for three days, because all plants use the energy they've gathered during the day to perform their nighttime duties. A three-day exposure will definitely earn you some extra resin, but after the first day your plant will start to lose that energy it's using to make trichs. A gradual process of light reduction will likely ensure that your plant has plenty of stored energy to produce a whole lot of trichome in the dark. However, it may be that sticking the plant in the dark for an extended period causes such stress to the plant that it begins a much more rapid trichome production than usual (survival mode). Since we can't know for certain, the obvious solution is to do both. Reduce the lighting by 2 min every day and when the plant is fruited, mature, and ready for harvest, let the bitch sit in the dark for a few days. I bet it will work just fine... Hmm... I think I might test this hypothesis.
IT IS ESSENTIAL TO NOTE THAT GENETICS MAY PLAY A HUGE ROLE IN THIS!!!
While all strains do produce resin more vigorously in the dark, it may be so miniscule as to be entirely unnoticeable. It just depends on the plant. Either way, any increase in potency is a good thing, and light reduction saves you money!