I wouldn't wait too much longer before you start flowering them. It is already September and it takes 7-9 weeks of flowering before they will be ready to harvest. Bringing plants indoors and out is okay, but be careful. When a plant is outdoors, it will bring bugs and pest with it indoors.

I was planning on experimenting with vegging a couple plants this winter and spring for 5-6 months before transplanting them into the ground in the summer. It would be cool to have 6 foot plants in the ground in may. I don't know if it would be worth the extra effort put into it though.