Do you have a scope Highside, so that you can check the trichomes. That will give you the ideal time to harvest. If you like a more heady high, I'd suggest harvest once they all go from cloudy to about 15-20% amber in color. They will mature a bit more while they dry. This should prevent it from being to much of a couch lock high. If you want that aswell, maybe harvest the top buds at 15-20%, and leave the lower ones till they hit like 30-40% should make a noticable differance.
I harvested my last grow at about 35-40% and they were a great smoke, but I can't tell you how many times I fell asleep on the couch at night. Or if I smoked it during the day, it was very tiring, I needed/wanted a weed nap.
