keep it in the dark any longer it'll die and rot on your branches.
judge your trichomes, get some picture references from google image and various forums.. or here too! Maybe it's my eyes, but that doesn't seem to be quite enough magnification.. maybe if you get up close with your eye it works better?
anyway, darkness is only important relative to preventing photosynthesis leading up to harvest. If it "seems" to help development at top of canopy, then it is more likely your lights are too hot -- either heat or photons, both are energy that can do this. you are likely evaporating trichomes off the top.
if doing it just because you read it somewhere, i'd tone it down at the least, if you want to continue doing it. 36 hours is about as long as it takes.
the theory behind the harvest thing is that it prevents biological processes related to photosynthesis.. Catabolistic processes take place (may have made up a word there! BWAHAH) like breaking things down to be used in sugar, then anabolic process like building molecues for internal development take place. supposedly this is bad for taste.
i do it just in case, because all i have to do is harvest in morning to accomplish the goal.. no big deal. starving the plant of light for 2 or 3 days isn't a net positive in any context i can thinkoff of the top of my head, unelss you burned off triches, which doens't look to be the case, fwiw. i speak mostly in generalizations, because there's all sorts of data missing when answering questions - no fault to anyone invovled.