Well, since you asked:
The bags don't leak. It's all the little air line fittings. I installed these Air lift bags with onboard compressor and dual gauges in 2009 on my 3500 SRW. I took them off in 2011 and put them on my '05 Dually. I've had the manual inflation schrader valves stick open slightly a few times causing a leak. One of the T push locks under the truck had a leak in it. Lately, when I noticed the compressor short cycling a lot I found a leak at the factory brass T on the back of the gauge assembly. I cut that back and put the line back on. Checking for leaks again reveled a leak where the line goes onto the bleeder valve to drop the pressure. I decided to do away with the little brass fitting and ordered some push-lock Ts. I installed them only to find that one gauge fitting is now leaking. So I've got bleeder valves, gauges, and fittings all leaking.
I'd consider replacing the whole gauge assembly but they don't appear to make that one anymore and anything comparable is close to $200.