They don't need it as such, but for real cold nights, you can. Day temps should only be 28 on the hot end, and if night time temperatures are provided leave it to 26.
Leave it on, it will aid in digestion and make them more active.The temperature should be around 30 degrees at the heated area so reducing it to around 24 would be good as it will simulate night & day as well as keep them relatively warm.