Man, there is a joy and a thrill to coming home from work everyday and looking at the triches and seeing if they are ready. The microscope is $9.95 at Radio Shack, and if you examine the trichs, you can compare the different highs.
I harvested my top buds and waited a few days, waiting for the trichs on the lower buds to change. Then I harvested them. AND i labeled them in my jars. What I enjoy is having the different kinds of high, based on the trichs and when I harvested. On Saturday morning, I can smoke a CLEAR Trich bud and I get high, but I get creative and energized too. Saturday night, (and every night) I can drink a few beers and smoke some of the dark trich bud and I get the HEROIN effect, like I am glued to the sofa and my brain quit working.
Yes, you can harvest them anytime you want to harvest them,and you can use as a rule of thumb, the stigma colors, darker being better. BUT, you will miss a lot of the fun, and joy of knowing precisely what you have to smoke. .