Many previous posts on this. It all depends on how much your rig weighs, and especially how much of that weight is placed over or rear of the rear axle. The airbags have a maximum psi of 100 psi, and you should never run them "empty"
Always keep 10-20 psi in them, don't let them go "flat"
Most run around 50 psi, but if your loaded , 60-70 psi may be the better psi. You will have to experment to get what is comfortable for you. Start at 50 or so and go up or down 5 psi at a time till you find what's right.
Be aware, the airbags themselves are fairly small, and you can overfill them VERY quickly, from flat to over 100 psi in a matter of 10-12 seconds or so.
When you add air, just kind of "blip" them a second or two at a time.
Steve & Cheryl + Charlie & Casey, our furry kids.
2012 Forrest River Lexington 283ts
Toad, 2013 Subaru XV Crosstrek