I determine if its done by looking at the plant overall, are all of the hairs amber and sucking back into the bud? are the lower fan leaves starting to yellow? I usually have an idea when its going to be done by looking at the genetics of the plant as well, if it's indica it will be done flowering earlier, 7-10 weeks, and sativa can be much longer anywhere from 9-14 weeks. By looking at your pictures I would say 2-3 weeks left. The longer you wait the more trichome development you will see. Checking the trichs for cloudy/amber isnt always the best way to determine if its ready to harvest. Some sativas don't even get amber trichs. -chron