I had two cats as a kid, and the day one of them hid somewhere to die from undiagnosed cancer was the day I learned that they'll just secretly go somewhere else :( She went under the basement stairs near the litterbox, and when I ripped the stairs out to get to her, I learned what a bunch of old cat pee and poop smelled like. I got much more serious about cleaning the litter box after that incident, and it's the reason why I'm waiting until I'm good and ready before getting another cat.