Last thing on the subject.........it appears to me it will help terpenes but not increase resin quantity, as everyone quotes 1 study from 30 years ago. No one has been able to duplicate those results in all that time. See below.....
My thought tonight is I'll continue to use it sparingly daily until harvest, but in very small doses. As Shane said in the last video, this could all be a marketing ploy by light manufacturers.
I'm using a UV light system too. My 3rd grow using it and have passed beyond trials and the baby steps and am now committed to full on no holds barred use of it.
I'm at 5 continuous hours per day, turning on at the 6 hour mark and turning off with one hour left to go in the 12/12 light cycle.
I'm about as hands on as it gets. I have no time for studies and reports to make a decision for me, I just invest and do and figure it out for myself if it's a good choice or not. Or really I should say my plants decide and I follow their lead.
My first experience with it was several years ago using the Powerveg lamps from Eye Hortilux. They're UV enhanced T5HO in veg spectrums.
These lamps will either stress plants or get them grow way better than any other T5HO on the market. The key was they needed to be higher than common T5 to get the better result.
Later on I got into it with flowering like many others have because if anything is rumored to increase trichs I'm usually first in line for it. Potency matters to me above everything else when it comes to growing pot.
First run was baby steps with no enhancements to report but did notice by accident having a spider mite infestation the mites avoided the plants under UV as if they were poisoned. I don't consider UV to be a 100% effective thing to deter and kill mites yet but I saw enough that if I get mites again, they're getting nuked with UV as my first option.
Second run I had zero bugs so could not say if it was because of UV or not. I did not notice an increase in trichs but the plants did produce a lot more oil than usual with some plants even oozing oil.
It also toughened them up giving a hardy look more like an outdoor grown plant than indoor grown.
Third grow which I'm on now using UV and the training wheels are off with longer on times and lower down on the canopy. I have 150 watts of UV raining down on this garden for 5 hours a day and started it at week 5 of bloom. Still no adverse effects but the same tougher looking plants, glossy leaves, increased stink and flowers looking to be full of greasy oil is flashing again but still no increase in trichs.
I haven't seen any damage to make me want to stop using UV but have also come closer and closer to the idea of using it solely for increasing trichs is more bro science than fact. But the interesting effects of increasing hardiness, terps, internal oils, and a bug deterrent is enough to keep them on in my room for now.