At least another 3-4 weeks, maybe longer.
Stop giving nutrients when there are about 95% brown pistils and harvest when there are 98-99% brown pitils, this will put you in the "10-30% amber trichome" zone without having to look too closely.
No need to drown your plants with huge amounts of water, just stop all nutrients 10-14 days before the expected harvest time and your plant will flush itself. Just give plain water, in normal amounts and at normal intervals and this is all that is needed for a "flush".
Flushing could really be thought of/renamed "nutrient witholding period", as this is the time when you want the plants to get rid of any nutrient salt build up in their system, so stopping fertilizing achieves this without running gallons and gallons of water through the pots, which just causes hyper saturated buds that can then develop mould problems when drying after harvest.
At this stage I would actually suggest increasing your feeding slightly, especially P and K, as your plants will need the nutrition to finish growing their flowers and by the look of things, they are already hungry, as evidenced by the many pale/yellowing leaves.
Hope this helps, Organoman.