if im on 12/12 for a while and add even more darkness will this stimulate bud?

also if i make it colder?

there are a few strains that ripen better with a 10/14 on off time like white lights i beleive. but not knowing your strain i would stick with 12/12.

colder is definately an option because it will simulate the cool temps of fall coming.

I'm intriged on how you would make it Darker. Wesley Snipes Dark?! Just kidding. Colder isn't the best for plants, plants should have around I think 65-70 degree temps at night? Something like that. Should, not have to.

Making it colder will not speed up bud growth. It will just make the bud turn purple.

I wouldn't go too low in temps, and I also wouldn't cut your daylight hours until right at the end. Like maybe the last week or so because the numbers you get from breeders on flowering time is based on 12/12. I would think that if you did it too early it could diminish your total yield. I don't know how much it will help you, but I guess it's worth a try. I'm sure that if you search enough you could find someone else who has tried this.
These are just my opinions, I have never tried to do this.