Autos ? 3 months and 22 days later.

Limited experience with autos, but some take longer if they are the mega-yielding type. Figure the first 2-3 are vege and the rest is flower. You'd be ~11 weeks or so at "16." Still reasonable in some cases. Do you have a jewler's loupe? You can't determine trichome ripeness without one. Extra heat or too much light can cause pistils to continually form. If this is only occuring in the uppermost parts of canopy, that's a likely cause. This would also evaporate trichomes faster than they can form. So, if slightly lower in canopy looks nice and gooey and not throwing new pistils, judge the plant by those buds or raise lights and try to salvage the top a bit. If ripe below, i'd harvest, or at least harvest below then allow the top to have a bit more time, if you feel the need. If it's happening all over, then it's probably just still thickening up and you got one that takes a bit longer but provides more.