Toyota LandCruiser: will the engine wear out?

I'm thinking of buying a 1998 Toyota Landcruiser 4.2-litre turbo diesel ute that's done 200,000 km. I don't plan to use it for towing or loading it up with heavy loads, and two mechanics have told me that if the car is not used for towing or carrying heavy loads that the motor will wear itself out. Is this true?