I had a 159 2.4 JTDm Sportwagon for about a year. I did quite a few long journeys, but my commute was quite short, which sometimes stopped the shitty cat from doing a proper regen cycle. This would then put the whole car in limp mode and the Alfa garage would have to force a regen cycle.
Did this about four times and I gave up on it, mostly due to the terrible customer service at the Alfa/Fiat garage in Bristol at the time.
Their advice was to take it on a 30 min drive on dual carriageways at least once a fortnight for 20-30 mins. Errr, no!
If you do regular long journeys, you should be fine.
I ran a BMW diesel for two years after the Alfa on the same length commutes for two years with no issues.
The Alfa was lovely, but some of the buttons were horrible (especially the ones on the steering wheel).