When the pistils are browning the plant is the ripening stage, thats basically the only indication they reveal. New pistil can grow, and i've seen it happen myself. So the plant will have white and brown pistils...how do u know which ones indicate the plant is done? the white ones say its still not done yet, but the brown ones say it is? To much guessing going on in that equation. The trichomes should all be at the same stage unlike pistils and bud size/denseness. Sometimes when the top colas reach max growth, the lower parts of the plant will start to use all of the stored energy and nutes that were utilized by the top part that gets the most light where growth is optimal. So u get new growth at the bottom, even tho the plant is ripening, but the top part is done and so is the older growth at the bottom, New growth can throw you off, and u say to urself, oh i guess its not done yet because i have new white pistils, not true. The plant will keep producing becuase unlike in the real world, we control the thermostat, the plan will keep growing because u dont change any factors, but degradation of thc and other chemicals will happen becuase the plant utilizes them, we just cut them down before that happens. Most people harvest the plant as a whole, and there not going to let the big top colas degrade, so they chop it down even tho the minimal small growth at the bottom isnt done yet, not really a big deal unless your plant is really starting to pop buds at the bottom. It's better to cut it down where it counts, no point in letting the small bud sites finish when the mass majority off the plant is done. I prefer to chop when 80% has hit cloudy. It ensure that i hit the middle ground of the plants smoking characteristics.