I read a bunch of when to go from veg to flowering stage and it has not, I am sorry to say, been useful to me. The reason is that everyone references N weeks. Friends, comrades, brothers and sisters, my plant doesn’t like your timetables. I just topped last week after about 8 weeks in the vegetative state with about six pairs of leaves, plant looking very healthy except for some gnats that I’ve been dealing with using a commercial, organic bug juice (it has a lot of sulfur, which is fine because my pH is too high and the sulfur will lower it). Yesterday I trimmed the gigantic fan leaves to let the light get in everywhere. It stressed mildly an is bouncing back already.
All that said, what do you look for when you are ready to flip to flowering? I mean, what physical characteristic says “it’s time”? Is it the size of those spikey things in the nodes (It’s a girl!)? Is it number of buds? Size of cola? I just don’t know.
When I get a chance I’ll post a picture of her if that will help in answering the question.
BTW, I use a timer for light and I can set it in fifteen minute increments, so when I lower the light, I’ll do it fifteen minutes a day maybe every other day. Yeah, I know I’m being slow, but I have a ten gallon container for her and about three more feet of height she can use before it gets too close to the light. I think my grow space can handle a five foot high plant.