When my Twinkle was alive I used to ask that question many times. Cats were foreign to me and I could not understand why he would disappear for hours on end and not come to hang out with me. Some days I would get terribly afraid he had disappeared for good , only to find him curled up and asleep is some corner some time after. I have since learned that cats sleep for at least 2/3 of their lives. It's a shame his life was so short. Do you worry about your cat's sleeping?