Personally I'm not sure if it's a one size fits all answer. My understanding is that it depends more on the type of tub in the rack. Like if it is a brown, black, anything non -see through that passes no light (so the tub would be pitch black day or night) then having a hide is less important. I was just talking to a former pb breeder yesterday about this same thing and he said he didn't bother with the hides unless they stopped eating or seemed stressed. I am a big believer in holding to core husbandry as the animal is small so I give all my younger bp's two hides one on the warm and one on the cool. I give my larger bp's one hide in the middle that they sort of move around back and forth depending on what they want.