How often should I change my stock air filter?

I own 2011-2012 Ford Crown Victoria and I live in Riyadh, Saudi Arabia, which is known for the huge amount of dust in the air, to put it into perspective a car would gather the same amount of dust on its surface in one week the same as a car in any "normal weather" country would have gathered in a month or two.
So should I change in the manufacturer s recommended service time period or follow some short time period, even though it does say in the manual if operating in dusty conditions check frequently and change if necessary but I m not sure how necessary is necessary. One more question; if operating in these dusty conditions, is just blowing pressurized air onto the filter (when it s out of the air box of course) enough?

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