My deremensis could handle hot temperatures for short period, and warm temps for extended periods - IF they had a cool night. They seemed to do fine wit warm days if they got a cool night.
I could not get my animals to live past 2 years. They were in perfect health, and just got slow, fat, stopped eating, and just dropped dead. I suspected the problem was in the temperatures. I was living in Raleigh, where hte summers were hot and the winters mild. The daytime temperatures were often warm in the room - 80's. At night, during the summer, the temps usually stayed warm, never below 70's.
The problem was in the winter - I was unable to get the temperatures down cool enough at night.
I moved ot the mountains, where it's always cool at night - even when it's 95 degrees in the summer, it'll be 65 degrees at night. I have to heat their room in winter. They seemed to thrive when night time temps were in the upper 40's-50's, as long as it warmed up during the day.
I allowed them to go through a really cool period for 2-3 weeks, then I increased the temps a bit. The daytime temps were cool too, 60's usually. They didnt' really do much - not so much eating, a little drinking. After I turned on their heat lamps (about the only time I used them), and the day temps went up into the 70's, they began to go nuts - red lips, increased activity, courtship, mating, etc. - usualyl after a week ro two of warmth and lots of food.
They would come out of the 3-4 weeks of cool temps much skinnier - they clearly lost weight. This was the key that I was doing something right. I could NEVER get deremensis to stay lean - no matter what I tried. The key was allowing them to survive off their body fat for a while at low temperatures. At higher temperatures, a hungry lizard doesn't simply burn its fat, as its body tries to store every bit of food it gets - further contributing to the liver problems!
By allowing them to fast, and lose the extra fat, I was able to keep them much longer - until some coccidia ruined it all. When my females developed eggs before, they filled the body cavity - 40+ eggs, they could barely move even with underdeveloped eggs! Most refused to lay their eggs - they died eggbound ( a big problem with the species).
The females that underwent a cool period developed much smaller clutches - 20-25 eggs, I think. One laid them, the other did not - she showed no signs of needing to lay eggs until I saw some laying on her cage floor.
There's theories why they don't lay the eggs themselves like they "should". Some thing they use a premade burrow from another animal. I wonder if they dont' have burrows themselves, like montium, for escaping the coldest nights. They seem to lay eggs when the keeper places them in a pre-constructed tunnel. So there's that possibility.
My problem was not being abel to really devote to them the time and effort needed. I always had everything just so close to being right - but never had luck getting eggs to hatch. Every female I've had did the same thing - they made no effort to dig, or even give me an indication that it was time. I found eggs popping out of them, and if they were able to lay them or not, they never hatched. All were fertile, but they went bad. too much time in the female.
I've promised myself that when I get into them again, I will not make the same mistakes. I think I've made them all, so I should be in good shape!
I'll keep it simple. 
