As long as it's been maintained with the correct oil and on time, then they'll last for over 250k miles. It's a great engine, with plenty of torque and fuel economy. The TD4 without a DPF suffers from less exhaust type issues, and is rated at 160 BHP. The DPF version can suffer DPF issues (like many DPF cars), and has slightly less power at 150 BHP.
There is also a 190 BHP SD4 engine, which had DPF and was only available in with an automatic gearbox. It's the same engine, just tuned for more power at the higher end of the rev range.