Our bunnies have a general routine, but when I was away at half term in February, my husband was still working and so looked after them. He is a shift worker and they had their tea/treats at hubby's convenience; sometimes at 3am and they were fine. They had unlimited hay of course as he made sure they were well stocked up by leaving extra stuffed loo roll centres and loose hay by the well-stuffed hay rack. Once we were back, there were no problems at all.