It is one of them things mate am afraid, where ever you fit a mechanical component to anything there is an inherent risk of that component failing.
When you think of what a turbo goes through, then you soon realise that they actually are very sturdy bits of kit. Every journey you do the thing spools up and down hundreds of times anywhere upto 100,000+ RPM to generate the boost the driver demands and they can heat up to a good 200 deg C as well, hotter still on petrols. I've seen turbos glow red hot before no problem. And then there is the pressure they generate which will cause expansion of joints etc, more so on dervs as they boost higher than petrols.
And they often easily do this over a life of 100,000 miles or more.
The turbos I believe are made by Garrett, the biggest name in turbos and make them for everything from the Ferrari F40s all the way through to turbos for boat engines, so they know how to make a turbo!
It come sometimes just be a little bit of luck of the draw with them though, if something has happened in the cars passed life that has affected the oil feed or air quality to the turbo this could have shortened its life somewhat.
A degree of mechanical sympathy can go a long way too, if you drive it like you stole it all the way to your front door and then shut the car off your turbo will be burning hot and you cut the oil to it, so it'll dry out. If though where appropriate you take it a bit steady and arrive calm and gently at your destination you've given the turbo a chance to cool whilst still having oil pressure in the system to allow the bearings to be effectively cooled and lubricated.
Remember turbo timers of the old skool RS Turbos, R5 Turbos and alike are doing the same thing!