Does the chassis have air bags now and you are replacing them or will this be an addition of some sort? If an addition, e.g. on a solid front axle chassis, I think it will help only if you currently "bottom out" at times. Otherwise the air bags probably don't come into play.
If you already have air bags (e.g. a P30 chassis with air/coil IFS) then replacing the bags helps only if one is currently not holding pressure. Adjusting the air pressure will affect the ride, but merely replacing a working bag does nothing.