I've brumated my snakes most years, but didn't last year. The only difference I could see was that last year, I really didn't know when the females were ready so I had to introduce the males every few days for several months with some of them. And a few didn't breed or laid all slugs despite several successful matings because the timing was off.
Being in the location I am, I have to use the outside temps to determine when I put my snakes down for brumation. Three days ago, we had temps in the upper 80's, so I'm waiting for the seasons to change and winter to actually set in down here before I even take my snakes off food. And I can never tell from one year to the next if the temps will stay cool enough. I've had a few winters where the temps were in the 70's for a week or two, but luckily, it stayed cool enough at night so they didn't get too warm and drop too much weight. And other weeks, I had to add some heat as temps went below freezing.
I've brumated in various places available to me over the years...outside on my back porch, in my bedroom closet, in my Mom's garage, in the bathroom (I swear that has got to be the coldest place in the house)...all depending on various circumstances each year. This year, I'm thinking of using the large shed I inherited from my Dad.
Where space is a concern, you can place several snakes together in a tub, just don't mix the sexes and make sure the sizes are fairly equal (ie...a 200gm male in with three 450gm males is not a good idea). Apartment dwellers in the northern/cooler regions can find the coldest place in their apartment (next to a window or a balcony, a closet, under the bed, in the bathroom) and brumate there. Depending upon what temp you keep your thermostat set at during the winter, the cool spot in the apartment is usually just fine to brumate snakes at. Temps constantly in the low to mid 60's is just fine. Depending upon the location of the cool spot, you can shield that area from the warmer parts of the apartment with blankets, etc.
