It basically comes down to this... The faster you move from veg to flower the lower your yield is gonna be.
I moved my two from veg to flower after about 4.5 weeks. They were roughly 10.5" tall, full, and healthy. They are doing great in flower but looking back I should have veg'ed longer as I have the space.
You just have pick the right time to max your yield, there is no math equation based on time.
Think of it this way, if in the end you would have waited longer and maybe bumped up the yield you now have a great reference point for grow 2.
Good luck to ya