I began noticing in the month leading up to the repair, that the on-board air compressor would run longer and more frequently when the car was started. Once in a while when idling in traffic, you would hear it kick on for about 10 seconds. Now that the pair of shocks were replaced, it is not nearly as frequent to hear the compressor kick on. The rear bumper is now level. i do not distinctly remember any event that led up to the need for this repair, but I have hauled a trunkload of landscape pavers with it, prior to needing the repair. The repair took less than an hour for both shocks once the guy just the LeSabre on the lift. He charged me $50 and the shocks were about $80. The good thing is, I won't be wearing out the compressor by letting it go. No idea what that would cost to replace, but it would probably be more.

Update from Jan 31, 2015: The right rear shock is leaking. Now have 123,456 on the odometer. This was observed when I took the car in to get an estimate on another issue. The airshock is now 4+ years old. Replacement cost for the part should be $0 for the part, but the labors on me beings I use a personal mechanic. He is combining this work with a much bigger job