I worry about my kitties only because they are destructive. I worry that they would break something and get injured on it. When I took a weekend trip I was only away for 2 days and 1 night but I still had a pet sitter come over and check on them to make sure that nothing had been destroyed. Even if they weren't destructive I don't think I would leave them alone for 4 days. I think maybe a weekend would be the longest I would go for.