Re: 57 degrees and most of the girls are staying inside today.
I'm a 2nd year, for what it's worth. In Holland, 2 deeps is plenty. And I am sure your bees are fine, at least from temperature. Mine are out and buzzing all over this morning, at 68, the sun finally came out. Their main effort is to try and get the stores from my little nuc that has a small swarm in it, and they are failing, so hopefully they'll go find some pollen soon. They are in the pond getting water, and just bees in the air everywhere here. I'm in Fort Worth. We got pretty cold this past weekend.
(my staple gun and some window screen are causing their fail.)
And it is not a great idea to open the hive when temp is below 65. If necessary yes, but if you have a feed jar opening or other way to peek that would be better.
Bees in winter - new phenomenon, but I've got them... So far so good.