I'm not sure what litter you use, but I use newspaper and sometimes I have to clean it out twice a day.. atleast at the end of every day. I think 4 days might be a little too long, just with the factor incase your bun goes into statis, then you can't moitor the poop level. Also, it might start to smell and get uncomfortable for the bun with soiled 4 day old pee and poop. I clean my buns cage out regularly, because i'm a statis-maniac, and they're inside.