Two of mine are in a permanent grass run of about 6ft x 20ft (as seen in Pea and Pod's picture). Because it's so big, they just poo down one end, which I've slabbed and you only get the odd bobble on the grass which I rake up. They keep the grass well chewed down so I don't have to mow it but I do keep it watered in the summer because it's under trees and gets very dry. They love it. Last year, they dug a huge tunnel in it. It's all under/overwired and as I've put fresh turf down over the years, the level has gradually built up so they've got about a foot of soil to dig in.
Flora and Parsnip have a shed with a 5x5ft run at one end and a 6x3ft run the other. I tried to turf the 6x3 run but because of it's small size, they just pooed and wee'd everywhere and I couldn't keep it clean. It's now slabbed!