Portable vs On Board Air Compressor?

I have the Viair mounted behind the back seat, bought one of those 5gal. Tanks for filling tires and mounted on the frame under the bed of truck (2015 f350 ) ran an air line to rear and to front of truck.Now I can fill my tires and my bags no problem. You need the constant duty compressor for filling tires otherwise your pump will shut down after so long a run time.