I think it's a very good question as I also wondered about the life cycle for an air ride suspension. Fortunately, these types of systems have been around for a while and you have a 3yr./36K mile warranty.
Based on good experiences with an '03 Allroad (put 34K on it), our Touareg (currently 136K on it), and now with our GC (no issues thus far), I'd say chances are slim that there will be problems. BUT, it could happen. So, for my peace of mind, I've always bought extended warrantys for my vehicles.
It all boils down to the amount of risk that you feel comfortable with.
Enjoy the car.
I'm a former allroader as well. I've had two allroads with these systems and no major issues. 102k miles on an 04, 65k miles on an 01. I am a bit addicted to air suspension after having the allroad and honestly would not have bought this Jeep without it despite the maintenance risks of owning a system like this. I'll echo what henrysko said about minimal or non existent issues with air suspension on the allroad. I did replace the front bags on the 01 due to a slow leak when parked for a long time, but it wasn't really necessary. The Quadra-Lift system seems far superior to the allroad system thus far. Air suspension has come a long way in the past ten years. There can be problems, one difference between the air springs on the GC and the ones on the allroad is that they have placed a cover over the rubber "bags", similar to the Arnott Generation 2 bags you can buy for the allroad. This will ideally keep the dirt out for much longer which is a major issue for developing holes in the air springs (commonly referred to as bags) in the allroad. The main reason for this happening in the allroad is dirt, dust, rocks, etc getting into the folds of an unprotected rubber bag when the suspension is set on certain levels.
With regard to the extended warranty, I have yet to see anything in writing concerning covering the air springs, so I wouldn't count on it after 3/36k is out unless it is specifically noted in your contract. They are made of rubber, and rubber eventually is a wear and tear item that deteriorates over time. I would not be the slightest surprised if they are not covered by most extended warranties (as is the case with the Audi allroad and T-reg).
As far as replacing the air springs, I don't anticipate it to be rocket science. The only blip I see is refilling the system with nitrogen (non existent on the Audi and T-reg, they use air) Here's a how to for replacing the springs on the Audi allroad to give you an idea of what is involved with these systems if you're curious:
allroad Front springs: http://allroadfaq.com/main/index.php...sion&Itemid=67
allroad Rear springs: http://allroadfaq.com/main/index.php...sion&Itemid=67
My PSA on jacking something with Quadra-Lift: to properly lift the Jeep, you must put it in "Jack Mode" to disable the air suspension. The suspension is active all the time which means that it is always auto leveling. If you put the vehicle on a lift, on jack stands, etc without putting it into jack mode, it will constantly try to adjust and level itself until it gets back on solid ground. You can severely damage the suspension components if you do not put the Jeep in Jack mode, so if you take your Jeep anywhere to be serviced, remind them of this. Your Jeep will thank you. To do this, hold the suspension up and down buttons at the same time until all of the lights come on indicating it is in jacking mode. The instructions are also in the owners manual.