There is no set time frame to lower lights, nor is it a requirement. That concept came about years ago when people where using all those low grade, non efficient amazon/eBay light fixtures. Those lights had poor coverage, poor light penetration and poor light output.. So people would lower the lights to compensate for all that. The plants could handle it because of how inefficient those lights were.
The light you are using is borderline "highly efficient". It gets 1.8 umols per watt.. High efficiency is 2.0 and up. It's no amazon/eBay light. It's Mars most efficient light so far.. Mars recommends 16 inches away minimum.. Any lower and you'll probably fry the plants. So, if you did lower it, it would only be about 8 inches. Your plants will probably stretch 6-8 inches, so you'll just end up just raising it again. People that use quantum boards, cobs, and other efficient lights like the one you have, usually set the light at 24-30 inches away from the canopy and let the plants grow up to the light.
As a newbie, the one piece of advice I like to give to to take all the growing info with a grain of salt.. Chances are, their situation is not your exact situation and their answers/advice may not apply to you. ( lowering the lights for example, doesn't really apply to your situation).
