Well it's a bit more than that.. Depends on what strain you're growing. How much space you've got. e.g. 2 days ago I topped upcanned and flipped all at the same time. Plant was pushing side shoots right away with no stress signs. I had to flip, cause I grow Kali Mist, which is a 14 weeks flowering sativa, and with my 150W + 70W CMH HID it will take even longer. Also I have only 2 feet of max vertical growth so I had no choice but to flip it.
You are forming your plant to fit your space. I top for 4, but not to get 4 colas, but to get even growth on four different directions as I train them low.
I'd say flip time and other actions depend on how your girl have to look in your grow room at her harvest day
Cheers!