The filter on my euro 5 costs about £50. Fiat recommend change on a mileage basis only at 45,000km. I don't think I will be changing mine annually.
I doubt you would get to that mileage on the same fuel filter despite any "Reccomendation" Contaminated Diesel is quite common and generally contributes to
most breakdowns relative to Diesel engines.
I thinks it's been mentioned earlier in the thread about the cost of a MH and the relative low cost to maintain it, to me it's simple economics and prevention is better than a cure.