Depends on the strain, generally 6-10 weeks w/ some exceptions. If you dont know the strain, wait til half the white hairs(pistils) turn brown/orange. This is not the most acurate way, but unless you can obtain a 30x mircoscope to view the THC glands, its the only way. If you have the microscope, the majority of the glands should be cloudy, if the majority are amber, then you've passed peak potency.