I'd second what s130 said, particularly regarding going beyond the requirements & getting the oil & filter changed annually. I don't have a 500X, but we've had two TwinAir engined vehicles in the family (500 & Alfa MiTo). One had annual oil changes at around half the mileage interval (500), the other went the full 18,000 miles (MiTo). The one with the extra oil changes ran much nicer than the other, was less lumpy, revved more smoothly & didn't need two new actuator units in 35k like the other!
Might be nothing to do with the extra oil changes, but I know from owning an Alfa Romeo & being on the Alfa Forum where many of the cars are MultiAir or TwinAir petrols, they are on the fussy side when it comes to oil level, quality & spec, so an additional oil change would do no harm - providing you make sure the dealer uses the right oil - preferably Selenia. Not all dealers use it by default, which makes my blood boil, but that's another story!