Litter users - I was thinking of switching Cassie from clay to clumping litter -- right now we use Tidy Cats with either the blue or red stripe on the label and I'm not unhappy, but I'd like to change the entire box less often. I get the 10-pound bag of Tidy Cats at the supermarket because the monster bag (although a better bargain) is heavy! The shelter used clay litter so we've stuck with that all these years - is it too late to switch to clumping litter?