Not too sure, I have my pollen filter changed my on yearly service. There's been a bit of leaves trapped in there and not much else, and this was from a 8k to 19k service interval.
I got a couple of UFI pollen filters as prime add-on items on Amazon dispatched from Italy at a steal price of 3 quid each, ended up purchasing 10, enough for the lifetime of the car as they're at a very cheap price
Seems to have sold out now though. For filters, ECP can be ok with prices but sometimes it's extortionate with similar prices to Fiat, I'd recommend looking around online at a reputable company (but not eBay, can't be certain if it is genuine there).
I did notice Fiat are not configuring any more diesel engines for new cars but just petrol, probably with all the diesel-gate issues. Pretty sad to see them go as they're small but mighty - in my opinion anyway.