Checking the trichomes is often regarded as the best way to check for ripeness. Be sure to check the trichomes on the buds, not the leaves. Magnification is needed. I use a 15x jeweler's loupe. I don't use it much now, though, because experience and looking at the pistils (and other parts of the plant) works well for me. Just to be sure, I might use the loupe when the pistils are telling me harvest time is near. Not all plants are the same, however. We just harvested a long-flowering Amnesia Haze (sativa dominant) that had many white pistils on the colas while the trichomes on the buds told us it was time to harvest. It's still in the drying tent, but early samples are favorable.
If the buds are still producing white pistils, it usually means they're still growing. The buds have completely stopped growing when there are no white pistils at the apex of the cola. They're usually the last to turn. I don't advise waiting that long, however. We tried it once because we were curious and decided we should have harvested the plant sooner. It wasn't ruined. It just wasn't as potent as other plants of the same strain that were harvested sooner. It was pleasantly relaxing, though.