I'm one who gets my plants out of the house as soon as possible.
I carry my seedling trays out to my 8'x16' greenhouse just as soon as I can after they germinate, but I don't leave them out at night or when cloudy cold weather can't keep it above 55F inside the greenhouse. I have much colder weather to deal with than you do in MS, so night heating for me is not efficient until the night temps stay above 25F. We had a low of about 8F last week, and projected down to 18-19F at night in the next few days.
The key as Karen said, is monitoring for temperature. I have two remote thermometers (don't trust just one) in my living room that I glance at every time I walk by. My greenhouse is about 100 ft from the house, so I walk out to adjust ventilation as needed. I have automatic roof vents, but in full sun, those are not enough and I have a whole array of various sized wooden blocks and bungee cords to keep my double dutch doors open at various angles depending on outside temperature and wind. Even with outside temps in the 30'sF inside temps get into the mid 90's if it's sunny and the doors are shut. I realize that people who have jobs and are not home all day would have trouble with this amount of tweaking.
I much prefer the health and sturdiness of having my seedlings in natural sunlight, even if it's more work for me. But my light fixtures are old fluorescents, they only run a few weeks each year and I don't plan on replacing them because of their short window of use.
You should do whatever feels best for your situation. No sense in changing what works for you. There is no one correct way to so any of this!
