Hi David:
>Is this common for the piston ring just to wear away the vehicle has covered 92K
Yes>you did say that it can be caused by a leaking airbag
Yes
>apparent with perhaps the vehicle dropping to one side or dropping down very quickly
Sometimes they leak in certain positions, or when driving, although if the vehicle is wheel free, you can usually see the bags very weathered with the cords showing.
>Do you also know if putting the vehicle into access/crawl mode does this expel all the air
It uses quite a lot of air to re-charge the reserve tank back to full pressure, but a good compressor would do this in a minute or so.
If you leave the driver's door open, (to disable the height control)a good compressor should charge a completely empty system in approx 5-7 minutes.
>Is it possible to buy a service kit for the compressor??
Not that I know of, just a complete compressor.
Regards
Steve