ALSO here is a little info that was sent to me by another old school grower .it is a good read .just putting up some info i found useful .
......But it is a known fact that THC works like 'sunscreen' in glandular trichome heads protecting the delicate inner glands from light rays. While doing that job some amount of THC is lost every day to light degradation. That means that had the harvested plants been left under lights another 72-hours they 'might' have seen some increase in THC levels but it would be impossible for it to have been as much due to some percentage of what was made would have been degraded by light.
Another factor is if harvested at the proper time during the additional 72-hours of light some percentage of THC would have degraded and turned into CBN, a waste byproduct of degraded THC, so there would have been some additional loss above and beyond that of just light degradation. The crop left in darkness had no increase in CBN during the 72-hours of darkness like the other group would have had if left under lights. It retained the THC it already had and added more. If the other group had been left under lights it 'might' have had some increase in THC but through light degradation and THC in fully ripe plants naturally transforming into CBN it would have been impossible for the possible increase to have been nearly as much and it is even possible there would have been an overall net loss.
A very important thing to factor in is that most THC is made during periods of darkness. During hours of light plants 'multitask' and perform many functions but even being under light they do have a limited amount of energy to use so it is allocated on a priority level and some functions receive more energy for what they are during the day than they do in periods of darkness and some receive lesser amounts of energy during the day than they do in periods of darkness. THC creation is one of the functions that receives more energy during periods of darkness when most other plant functions are stopped or their energy levels cut back to an absolute minimum.
Given 72-hours of darkness keeps the plants operating in darkness mode where THC production is receiving a larger amount of energy than it would during hours of light so THC production is maximized. Add to that there is no loss of THC to light degradation and no loss of THC in fully ripe plants naturally degrading and becoming CBN and that explains why even if there 'might' have been some increase of THC levels had the other crop been left under lights for another 72-hours there is no way it could have been anywhere near as dramatic as the largest increases and there would have been increased levels of CBN.