Debating the 'cold garage' method for annealing small pieces

I've been working out of my unheated garage studio in Denver, and last winter I got tired of waiting hours for my kiln to cool down for small pendants. On a whim, I tried putting finished pieces directly into a metal toolbox filled with vermiculite, then closed the lid and left it in the cold garage overnight. The next morning, they were perfectly annealed and stress-free. Some folks say this is risky and only a proper kiln cycle is safe, but after 30 pieces done this way with zero cracks, I'm starting to think it's a valid shortcut for small, simple items under 1/4 inch thick. Has anyone else experimented with alternative annealing for minor work, or is this just asking for trouble down the line?