I would keep that going until the bottom off the leaves start turning yellow and falling off so it can use as much nutrients it can, also make sure you have 1 day off darkness before flushing them
There are lots of white pistils, so you have a week or two to go yet. Why not pick up a 30X or greater magnifier or a USB microscope so that you can check the trichomes. It's the only accurate way to gauge whether or not they are ready for harvest.