I kinda go by what JohnnyGreenApples says, when the tricomes are about 1/3 to 1/2 amber and the rest still clear, it's time to harvest. If you wait longer the THC in will start degrading and your finished product won't be as potent.
Its not that it wont be as potent bro, and I dont mean to question you but I have never heard of it degrading. That could be very possible depending on the conditions your growing in though, as mold will eat your thc and make it crumble along with the buds.
As for the final product, it will still be as potent in my eyes
haha. I like to think it will just smoke more harsh and smell less pleasing.
I myself have had a plant go damn near 2 months over due for harvest and the light clycle turned back and it started to reveg and that is when it was put in under lights to finish out the reveged product, at that point after harvest happened there had been buds left on there from before reveg and those buds actually were just as potent as the new ones, the flavor was much more different than the new ones and the high was different but there are so many factors that come into play when you dont do things as they are intended to being done so bro!