actually, when you see trichs turning amber, that is a sign of THC degradation. Maximum THC is when heads are fully swollen and turning milky. Amber trichs will give you an increase in other canabanoids but for just THC, the maximum is when it turns milky and heads are totally swollen. I would pull them now as the last picture looks as if they are all standing erect, swollen and ready to go. If you want max THC I would say to pull them in the next 5 days as that is typically the window you will get for max THC. What is the strain and how long has it been in flower? The reason I say they look done is that I don't see any new growth at all on it. New new hairs, etc. At the end it is all preference and there are many other things besides THC which make a high what it is. So to answer your question as to max THC, it is when they are Milky.. As to whether or not it is time to pull, that is totally dependent on what you want out of the high. Later it goes, the more pronounced effect you will get from the other cannabanoids (CBN, CBD, etc)