My tincs are in aquariums with glass lids so the humidity is always high. The Leucs are in a 18x18x24 Exo Terra and both sections of the screen top are sealed off but there's still the gaps around the doors. I mist in the morning, noon, and several times in the evening. A lot of the humidity is dependent on the temperature. Right now in CenCal the weather is bouncing between the 80's and nineties and I haven't started using the air conditioning yet. There's not much natural moisture in the air in these parts...it's a dry heat.
By the way - How are my Arena Blanca tads doing? Did you ever get those Varibilis?