I had a 3500 with the manual inflate airbags. Every time I checked the pressure it would never be where I set it initially.
My current truck has Hellwig air bags with a firestone automatic remote controlled compressor. It allows me to inflate either or both sides
while driving. I mainly just set the psi where needed and it automatically maintain that pressure. I've noticed that heat, cold, altitude, and of course
different load levels all affect the pressure of the bags. Even going around curves the compressor releases and adds air to whichever side is needed.
If I run the maximum psi, the rear deck raises a few inches which helps off road clearance.
I mounted the small compressor in the rear floor storage compartment to protect it from water and dirt. Haven't had any trouble with it in the 4 years that
its been installed.