Well there must be a few hundred on the roads in 159s & Breras, even more so in the Giulietta with this engine. However there are lots of things that conspire against the turbo on the 1750 lasting a long time:
1) Direct injection - these engines are known for petrol dilution of the engine oil. We have seen upwards of 3% dilution with fuel when sending the oils off for analysis. Petrol is not a good lubricant...
2) Heat - there is a dirty great big cat strapped directly to the turbo outlet, all sandwiched in front of the engine, behind the radiator. Cooling is poor, it all gets really hot in regular use, even hotter when driven hard, probably because of point 3
3) 1.75 litres is a small engine for a big car. Consequently the turbo is working hard a lot of the time. More so than it would do on a 2.4 JTDM for example
4) Oil supply is poorly designed. A narrow pipe comes from the engine and passes near to the exhaust manifold, turbo exhaust housing and catalyst, this gets really hot and the oil inside this pipe can bake, especially when the engine is turned off and flow stops. Carbon in the oil burns onto the inside of this feed pipe, further restricting flow. Once oil flow to a turbo is restricted it is only a matter of time.
Best thing you can do is change the oil regularly. Let the car warm up nicely before driving hard and make sure the last few miles of a journey are steady to allow things to cool down. A little bit of idling when you arrive at the destination like on an old school turbo engine wouldn't hurt either.
Very valid points.
Turbo on TBI very easily gets red-hot - easy to check at night, enough is to give it a few pedal to metal accelerations, pull over open bonet and bright red is seen from under the turbo cover.
Regarding #4 mainly. Case of my friend's giulietta 1.4MA (in past Selenia Star PE was factory recommended oil for MA, not anymore) - at just 50kkm he got that turbo oil supply pipe very restricted with oil deposits - he replaced the pipe, and started using quality oils since.
So, IMO, it is not just construction of engine, which maybe in some places coudl be done little different/better, but I think the solution is just use of good oil. Of course since ecology (e.g. like ACEA C3) and economy (manufacturer's profit) are dominant, it is not that easy/cheap to buy such, most nonetheless called Fully Synthetic, use mainly hydrocracked minearal oil bases. True Sythetic bases like PAO and POE are small percentage of most of today's oils, though there are some oils which are exceptions ( I think Amsoil, Motorex, Meguin have some which are 5W40 ACEA C3 true synthetic). Some HC based oils are better than others, Motul Xclean 8100 is considered good HC based and Penrite Enviro+ even better as far as I read recommndations of alfa/oil geeks on polish forum.
One thing, you are concerned about supply pipe, but didn't mentoned the screw-filter. Why?
IMHO, this filter may be problem earlier than clogged supply pipe (which has much higer diameter). Filter has only a few mm (3-4?) diameter hole, and plastic filtering grid inside with tiny holes, and I'm sure dirt very quickly restricts oil flow there (which somtimes ends up with filtering grid broken, probably becaus of pressure)
Here is link to onle of many pictures of that screw - how it looks after 50kkm in Giulietta MA:
[Giulietta] Wymiana oleju, czyszczenie odmy, czyszczenie filtru modu?u MA. - Strona 26
in that thread, you could read (unfortunatelly it is in polish) about cases of filtering grid already in pieces after only 25kkm. A lot of people either replace the screw every say 2-3 years, some removed the filtering grid, others bought another output oil pipe screw and used it instead of supply side (it is similar but without filter).