When I'm done with one, it's ready for the scrapper. I keep them until they fall apart, literally. Average ownership for me is 10 years, I don't change RV's like I change socks.
I would say most totalled or older units are scrapped. A commercial shredder can separate everything, from plastic to cloth to aluminum to steel, all in one continuous process with each material put in a pile for later recycling. They eat engines and transmissions and rear ends whole and spit out little chunks ready to be remelted.
Way back when, I used to haul Chevy pickups from Pontiac, Michigan to Toledo to be shredded. Whole pickup trucks, tires and all that were assembly line rejects. I'd back a dump trailer into the dock with the tailgate open and they'd shove a line of trucks in with a hi-lo. I'd shut the door and take them to Toledo to get shredded, 10 at a time, every couple days. Went in whole, came out in small pieces.
I would imagine an old / wrecked RV would shred easier.