I would change it, if for no other reason than to establish a baseline for the future. It may well be the filter was never changed, so get a fresh start.
The Farr Eco air filter on my ISL is only marginally capable of the engine's max air needs (just meets Cummins minimum spec), so even a small amount of dirt becomes a performance limitation on steep grades. Mine uses the FAR 094973-007.
By the way, the same Farr Eco filter is often available with different suffix numbers, e.g. the -007 above. That designates a different physical inlet/outlet shape for the same internal filter. You probably need the matching suffix number to properly mate up with the rest of your air plumbing.
2004 American Tradition; 2014 Buick LaCRosse
Homebase in the Ocala Nat'l Forest near Ocala, FL