I also clean as soon as I see it. Their urine is solid (mostly) and bright white, so it's easy to find. Their poopies look like weird shaped substrate (I use Cypress mulch). I've learned that they do a pretty good job hiding it in corners, so I look carefully. I handle my 2 boys daily, so I see it when I hold them and change their water. Like others have said, the more you can notice and pull it out, the less chance for mites and such.