Outdoor is my jam...autos are not... but yeah you can do them outside in grow bags. Are you wanting to bring them in at night for temperature reasons? To supplement light? Do you have other plants going? The only thing with going back and forth, it greatly increases your risk of bringing pests in to other plants if you have them. Not saying don't do it, because I do it this time of year when I start hardening off the outdoor ladies... but I don't have other weed plants to worry about and they will be outside permanently in about a month anyway. They will likely not get as big outside as they would under 18 hours of light, and you should plan on doing something for pest prevention... what climate do you live in?