From what I know/experience is some breeders give them water and then no water at certain intervals. For example you give them water for three days and then none for the four other days. These are for ones that are in shoe/sweater boxes. For the adults, they usually keep water in with them if in more an arid climate. I give my baby horridum water on Friday and dump it out on Sunday. It also depends on how humid their container is and how messy their bowl is. If its messy I dump it out right away and change my water schedule. I try to keep the boxes as dry as possible to avoid skin problems while keeping them hydrated at the same time. It work fine for me so far.
As a side note, I went to the Zoo out here and saw a pathetic site. They had two Reticulated Gilas and a water dish that was too small for even a kingsnake. The bigger Gila was trying to soak in that little dish. Felt sorry for it.