No need to do extended darkness, it is BS/Bro Science and does not work in 100% of cases and with 100% of plants.
It happened with one plant out of a sample of 3 and thanks to the internet it became some sort of juju science.
The increase in THC was in the order of 0.0000000001%!
Putting my scientific hat on, extended darkness just causes a plants metabolism to cease being active and a plant with an inactive metabolism can not support or prevent trichomes from breaking down into worthless crap.
Don't do it would be my advice!
If you are determined to do this dubious stress treatment on your plant, right before harvest and after weeks/months of careful cultivation, yes, leave your system on.