I'm private and I keep a 6 year old spotted in a 70 litre tub, they aren't cows they don't graze. It may not be ideal but it's better having a smaller well heated enclosure than a poorly heated large enclosure I feel.
It's all about the equilibrium of husbandry, obviously we can't recreate the wild in our loungerooms/herp rooms so we do the best we can, whilst still providing the best husbandry possible.