It depends on how wide the temperature swings are and for how long. Burns can occur from extreme localised heat and digestion and immune system can be poor with too little heat.
It's always better to use a 'pulse proportional' thermostat and not an 'on off' thermostat if your heat source is non light emmiting. This will create a more stable hot spot because the thermostat will be regulating a constant power source instead of heating, cooling then heating again. They're good for heat mats and tape, radiant heat panels and ceramic heat emitters. It will also make your heat source last longer. If you use a bulb use it with a dimmer thermostat.
Also, it depends on your cage type. The best type are made from wood or plastic because heat and humidity aren't lost easily. If you have a glass tank maybe with a screen top you're gonna lose heat and humidity too fast.
If you're in the UK I recommend a Microclimate Evo thermostat. If you're in the US I recommend a Herpstat thermostat
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