It’s a little harder to raise chicks in the winter but I do it, normally for the same reasons you mentioned.
My 3’ x 6’ brooder is a permanent addition to the coop. The top of the brooder is my droppings board but the sides and bottom are made of hardware cloth. In the heat of summer I leave it pretty open, blocking off underneath to keep the hens from laying under there and with bins to catch the poop. In the winter I wrap it really well with 3 mil plastic and put a piece of plywood or cardboard on the floor to trap the heat.
I only heat one end. That end stays pretty toasty but the far end may have ice in it when it gets really cold out. The food and water stay on the warmer end. Even straight out of the incubator the chicks are pretty good about self-regulating, they pick spots that are warm enough for them. I’ve put chicks in there when the outside temperature was below freezing.
One of the problems with brooding outside is that you have to deal with fluctuating temperatures. Days might get pretty warm but nights pretty cold. By having a large brooder and letting the temperature vary across it, all I have to do is keep one end warm enough. If it gets too warm, they move further away. I don’t have to worry about adjusting the temperature.
When they are exposed to colder temperatures like this they acclimate faster than chicks raised indoors in tropical conditions. They feather out faster and just get used to dealing with cooler temps. I’ve had chicks raised this way go through overnight lows below freezing with no supplemental heat in my grow-out coop before they were six weeks old. My below-freezing was mid 20’s, not sub-zero. You might want to play that a bit by ear, but they really can handle cold weather once they feather out. In the right set-up, you can keep heat on for as long as you wish. They just need room to get away from it if it gets too warm for them.
So my answer to you is that you can move them out whenever you feel you can keep an area warm enough for them.