It'll double the lifespan. When the first engine goes tits up due to all the emissions bks on it, just jump in the back, you might get up to 80,000 miles before it's scrap then.
I saw a couple on a lorry the other day. I googled them and they are real. They at bought by bespoke coach builders.things like camper vans and car transporters. Males the options much more open for axles, suspension etc,