There is a corner of my basement (which isn't fully heated) that has a storage space built into it. Inside the temps get below 60F around late november, drop down into the 40s thru January/Feb, rising back up into the 60s around March. The lowest temp I've recorded there is 43, so they are in no danger of freezing. Outdoor temps here can get below zero at night in the pits of winter.
By October/November my torts are indoors all the time. I feed them until mid-november, then I start reducing food/light/heat.
I give them several soaks a week during this time.
They eventually stay in their hide spots all the time, usually late November/early December. If the temps in the corner are below 60F, I place the torts in ventilated rubbermaid boxes with slightly dampened newspaper. I check on them every few weeks, adding a slight bit of moisture to the newspaper if it is dry. I will weigh them during these checkups and examine them for signs of illness.
NOTE: Others recommend that you hibernate your torts in a completely dry setup. I did that last 2 years and noticed the torts were losing weight all the time. This year I made the newspaper just slightly damp to provide some humidity. They haven't lost any weight, and show no signs of respiratory problems from the slight increase in humidity.
I pulled my 1.5 year old out of hibernation after 60 days, just to be safe. He had lost no weight since the first day of hibernation, but has put on about 20grams in the last week.
I'll pull the adults out after about 90-100 days if the temps stay below 60 and they remain inactive.
This is my 3rd (or 4th?) year of hibernating torts, and all has gone well with some modifications of the above method.
My torts have laid over 20 eggs in the last 3 years, but have produced only one fertile egg that later hatched. I don't know what the problem is, other than I have only one male and maybe he isn't motivated enough.
Ed