Kebab's a bit strange in that he doesn't hoard or pee in his house, although it's big enough. He hoards in a hide on his shelf and pees in a corner. This makes his cage maintenance much easier as I rarely have to disturb his nest. I just check it every now and then. I got him when he was 2 and he had only had a little hut before then so I suppose he just got into the habit of hoarding away from his nest. I've checked his cage all over and didn't find anything. I replaced his hoard with new food.
One gerbil pair, Tilly and Wispa, don't seem to hoard at all. One of the other pair (Twiglet) is hoarding a lot right now. Not all gerbils hoard, but when they do it's often triggered by the onset of autumn - getting ready for winter. However her hoard is under several inches of bedding so I think I will leave it for now. Most likely if anything hatched, Astra would eat it pretty quickly. She loves insects and meat.