I just happen to have a room in my house that is friggen freezin' (by human standards). I brumate garters in that room, in the winter, making sure they stay somewhere between 50-60 degrees and turn off all their lights/heat and only ambient natural light from a window is coming in, and shut the room off from the rest of the house. There they stay for 3-4 months. Making sure they always have fresh water and 50-70% humidity. That's all I ever did. And I made sure to increase light/heat gradually over 2-3 weeks. Once up into the 70's, pairs kept together only had one thing on their minds - SEX! No sense in offering food at that time. They eat after successfully breeding usually. Never lost an adult like that. Lost a neonate or two, but never an adult.