Maintenance, maintenance, maintenance.
Garage near me had a woman come in. She looks at their recovery truck up on the ramp. "Not a very good advert for your business, is it?" Owner says "its being serviced". He said she looked at him like he was talking a foreign language. There are two types of people in the world that he calls repairers and servicers. The repairers fix things when they go wrong. The servicers rarely get to that stage.
If the vivaro has had regular servicing, Im not at all surprised that its lasted. Given that oil lubricates and clears dirt and swarf out of the engine, why are people surprised when their gearbox blows up after three years on the same oil and filter? Saves money in some weird world where repairs are free, I suppose.
Anyway, as Ive said before, any van you buy is either 100% totally useless or 100% totally perfect (if you listen to the opinions on this site, that is).