Should this air-filter should have been replaced sooner?

I bought this F350 2 years ago, with 6500 miles on it. Today it has about 18,000, so I figured it was time to swap the filter;).
I had -assumed- that since I had bought the truck from a regular Ford dealer, they had checked the air-filter. But I guess they decided not to, since it only had 6500 miles, but was 3-1/2 years old.
The first owner had it for 3 years and put roughly 500 miles on it.
The 2nd owner had it for 6 months and drove roughly 6000 miles.
I'm guessing is was the factory filter.
I'm going to guess, that at some time during the first three years, when it was mostly parked, some rodents moved into the air-intake.