Harvest twice? How much time for trichomes to change?

Wait until the pistils are 95-98% brown, this will give you buds with peak THC and terpenes. Letting all the pistils go brown will give you flowers with reduced THC, but with elevated CBD and CBN levels, producing buds with a sleepy and heavy body stone rather than a mind warping head high. So depending on which type of effect you prefer, let these parameters guide your harvest timing. At this stage you still have a while to go. I would suggest harvesting the whole plant at the same time, once you remove large portion of the plant, it freaks out and its metabolism is really stressed, meaning it takes ages for the second pick buds to finish and in my experience, they are never as good as the early harvest buds, possibly due to the freaked out metabolism caused by the giant shock of removing large portions of the plant being unable to support any further trichome development. Personally, I believe harvesting by pistil colour is far more indicative for harvest timing, as trichome colour alone can be misleading, as some plants will never get amber trichomes, while others will have 50% amber trichomes after only 4 weeks of flowering. Pistil colour will indicate the plants level of maturity precisely, as it is plant health which dictates trichome quality, not trichome colour. Hope this helps,.............. Organoman.