We moved to a new house two weeks ago tomorrow so our pet cat has been kept in and has been using a litter tray. Our old house had a catflap so the cat didn't use a litter tray. DH says that once we are able to let the cat go outside we can get rid of the litter tray. I think we need to keep it as we won't necessarily be able to let her out when she needs to 'go', either because we're not in or because it's night time. Who is correct?