would probably just leave them outside as bringing even a couple of plants in and out everyday so they get 12 hours darkness is alot of work unless you have a decent light like a high pressure soduim on a timer to put them under indoors they will do much better outdoors under the sun.
and plants continue to grow during the first several weeks of flowering so they wont remain at the same height, a 3 ft plant could very well finish being 5-6 ft tall.