He's running Bilstein shocks and the likelihood they would need to be replace is about zero. Unless you damage one and cause it to leak, they are good for 100,000 miles.
Most likely his feeling is due to having coil springs in the back. They can tend to make the rear feel a little more wiggly then leafs. New springs might help but the air bags will most likely work better if he is not planning a lift any time soon.
My .02 worth. YMMV
And a good .02 it was! Right on the money.
The shocks are newer, and damping is not a problem. The factory spring rate is. Especially with the front sway bar connected, because it straight up doesn't let the front suspension flex, all of the articulation all gets transferred to the back end of the vehicle, which is not subject to nearly as much anti-sway. Disconnect the front sway bar and she rides smooth as can be up curbs, up steep driveways at an angle, etc. Coming up my driveway at anything more than a crawl, my CB antenna mounted on the right rear of the vehicle swings back and forth and hits the body with the front anti-sway bar connected, but it stays completely still with the front anti-sway bar disconnected.
Putting just a bit more spring rate in the back has helped counteract the super stiff front sway bar quite a bit. It evens things back out, in terms of how much articulation is being allotted to the front suspension and how much is absorbed by the rear. And so far it has made the Jeep handle the utility trailer MUCH better, both empty and loaded. How will this impact flex off-pavement? We'll see. But even if it hurts it a bit, it is a worthwhile tradeoff for being better able to handle rear loads and to make everyday driving a bit more pleasant.
Eventually I suspect that a lift will get installed, even though I don't really need a lift to allow full flex of my 31s. What I do need for how I use the Jeep is a stiffer spring rate, so the bags are a perfect solution to that problem for now.