There are still quite a few all MAN fleets around that purchase outright. If your buying them regular to a similar spec and getting a subsequent good price then running and maintaining them right they are a very cost effective option against pretty much all other brands in the market place.
Keeping them for around 5-6 years maximum though/ or less dependent on higher mileage!
I think all modern trucks are fairly reliable if you know what your doing and have the right mix of people and equipment.