Background info...I have kept uros for over 10 years.
I have brumated my mali uros for years. The temperatures in the cages naturally are cooler in the winter since I live in Canada. The food is slowly decreased to allow the stomach to empty before they go into brumation. I leave the basking light on for a few hours each day in case they want to warm up. I leave a dish of dried lentils in the cage in case they need to eat but they never touch it. I also leave a dish of water (changed often) there in case they need some. (I don't have water in the cage the rest of the year.)
Doing this, they have always survived the winter but they do not produce fertile eggs.
I think with malis its necessary to hibernate them (cooler temperatures than what brumation calls for). The only problem with this is that if its not done properly you might lose your uro.