I don't think there is a rule of thumb with harvesting. It seems to depend on the plants and what the individual person prefers. In my experience, if you like bud that gives straight head high then harvest on the early side when trics are just getting cloudy. If you like more of a body stone or medicinal stone then you want to wait till later when the trics are starting to amber.
I am sure this as well will vary from strain to strain. If you want to try an interesting experiment, try taking some nugs now and dry n cure them properly, then pull some more in about 7 days and cure, then the last pull when the trics have all ambered (14days?) and cure them. Then test each one separately to see how the results work.
I have tried this in a limited fashion and the results were fascinating. and fun