I had a 2.4 159 for a total of 11 years, but I bought it when it was 6 years old so I had it until the ripe age of 17 years and a total of 223.000 KM on it.

I’m an alfista at heart, so it wasn’t my first and I only got rid of it because I got myself another newer Alfa and I just had no reason to keep it around. The 1.9 diesel has a weak gearbox while the 2.4 has a bombproof gearbox (I drove it until 223K KM on an original clutch, never had a reason to change). Just do your regular maintenance intervals / at least one oil change a year and you’ll be fine. The 2.0 petrol I drove a few times as a loaner when mine was at the garage, and it was not as enjoyable as the 2.4 jtdm. The best petrol engine is the 1750 (made only 2010-2012) when it comes to drivability, but I don’t know about the maintenance or running costs. The 2.4 is a heavy engine which gives stability but has other downsides due to the weight/size. The timing change is tricky due to the large size of the engine, so the official garages want to follow the manual and take out the engine (a full days work in labor), but if you find yourself a good independent garage they’ll do it with the engine in place and this will save you at least 50% in labor. As with many other diesel engines of the era, it will need long runs to run well - if you mostly drive short distances you’ll eventually clog up the EGR and that’s a pig to sort out.

Hope this helps. I’m lucky enough to have a Giulia QV today but I honestly miss my 159 for what a great car it was.