There’s more factors than distance covered when it comes to diesel fuel-injector lifespan. That said, modern, common-rail diesels do seem to work their injectors pretty hard, so it’s possible that yours will be ready for replacement at 165,000km on the odometer.
Other elements that will contribute to injector wear are fuel quality, dirty fuel filters, the overall condition of the system including the fuel pump and simply how well the vehicle has been maintained generally. How it’s been driven will also have a bearing on injector life, including whether it’s been used for highway travel, urban running and whether it’s been used to tow relatively heavy loads.
Fuel-injectors can be rebuilt or reconditioned, but the trade reckons that a reconditioned injector will have about half the useable lifespan of a brand-new replacement injector. As for injector servicing intervals, I’d be guided by what Volkswagen says in its factory service schedule.