You can get them to go into brumation pretty much at any time by adjusting temps cooler, and making day light periods shorter. Some may go with this early simulated brumation, and some will just sit up as if to say hey turn up the damn heat in here and will not go down until they are ready.
I personally put mine down late September early October when they start showing me the natural signs that they are ready to go down. When I notice the signs I take them in stool samples to make sure they will not be sleeping with heavy parasite infections, and if clear I shorten the daylight cycle and slowly cool the cage till they are sleeping most of the day. At this time I pretty much cut the uvb light and keep the cage lit with a low watt heat bulb for 6 hours a day. If I see them up I give them water and make sure they are ok, and usually they will go back down to sleep. early-mid Janruary I start changing the light cycles and temps to stimulate the coming of spring, and slowly adjust the days longer and hotter till they are awake. Once they are awake I start feeding the females heavy for the coming breeeding season. This year Candy & Anna started forming eggs only a month and a half out of brumation.
Here is a great site about brumation and what to expect. Just copy and paste into the browser.
http://www.biology.lsa.umich.edu/research/labs/ktosney/file/BDbrumate.html
-----

Webshots photos
www.Mystical-Dragons.com