If you leave the couch outside, the cushions may vanish.
A roofer told me that they "harvest" cushions from abandoned couches as the cheapest & easiest to use "safety" equipment to use on roofs. Sitting on the things makes it almost impossible for you to slide off a roof (well, unless it is really steep, I suppose). The cushions tear up and wear thin quickly due to the rough surfaces of shingles....but they can bump & slide their way from place to place on the roof quickly, without too much risk of continuing to slide - as soon as their weight hits the bare foam rubber cushion again, they STOP moving in a very short distance (a finger width or three, at most).
Me? I'm 55 and I neither bounce nor heal as well as I did twenty years ago, I'm not going out on my roof (first or second story)!