If you are trying to judge with the pistil “hairs” colors alone, you might want to wait until nearly 100% of the pistils are amber or orange-ish, or brown-ish. This indicates the “buds” are done, and with no new “bright light color” hairs(pistils) showing up, this usually is indicative that the new pistilate/calyx (“buds”) has come to a crawl or complete stop. But by waiting this late you have a higher chance of getting the “couch lock” with a lot of strains, and even some self pollination from latent late flowering hermaphroditism, which is actually quite common in many strains. The only way to know for sure is watching the trichomes, get a jeweler’s loupe, I like at least 60 times magnification.