If cared for correctly, a 200tdi engine is so well constructed that it will last forever.
Overengineering was cut down on the 300tdi, but it's still a powerful engine.
Td5's motor is much more refined, but it's not perfect. Once the problems that LR intentionally introduced are fixed, however, it has the potential to be a game-changer.
Personally, I miss the original 200tdi.